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The Offshore Marine Environment
of Ascension Island, South Atlantic:
Scientific Review and Conservation Status Assessment
Report to the RSPB
by
Sea-Scope
Marine Environmental Consultants
October 2015
Front cover: Blue shark Prionace glauca. This open ocean species is one of the main shark species to be caught
as bycatch by the commercial longline fishery targeting tuna species in the mid-Atlantic.
[Image: https://upload.wikimedia.org/wikipedia/commons/e/ea/Prionace_glauca_1.jpg].
The Offshore Marine Environment
of Ascension Island, South Atlantic:
Scientific Review and Conservation Status Assessment
Author:
Robert Irving
Principle Consultant
Sea-Scope Marine Environmental Consultants
www.sea-scope.co.uk
This report should be cited as:
Irving, R.A. 2015. The offshore marine environment of Ascension Island, South Atlantic:
scientific review and conservation status assessment. Report to the Royal Society for the
Protection of Birds (RSPB) by Sea-Scope Marine Environmental Consultants. 115 pp.
The Offshore Marine Environment of Ascension Island, South Atlantic
Contents
Executive summary ................................................................................................................. iii
1.
Introduction ................................................................................................................... 1
1.1
Ascension Island - geographical context ................................................................... 1
1.2
Ascension’s nearshore marine biodiversity................................................................ 2
1.3
Island governance and history................................................................................... 3
1.4
Proposals for a Marine Protected Area ...................................................................... 4
1.5.
The scope of this report............................................................................................. 5
2.
Collation of scientific knowledge ................................................................................... 7
2.1
An overview of the geophysical and oceanographic context ...................................... 7
2.2
Commercial fish species ......................................................................................... 11
2.3
Non-commercial fish species................................................................................... 16
2.4
Sharks and rays ...................................................................................................... 23
2.5
Cetaceans ............................................................................................................... 29
2.6
Turtles ..................................................................................................................... 32
2.7
Seabirds.................................................................................................................. 36
2.8
Marine molluscs and other invertebrates ................................................................. 40
2.9
Seamounts .............................................................................................................. 43
2.10
Deep-sea and pelagic biodiversity........................................................................... 49
2.11
Oceanic microflora / microfauna .............................................................................. 53
3.
Conservation needs and threat assessment ............................................................... 54
3.1
The sustainability of high seas fisheries .................................................................. 54
3.2
Offshore impacts on species also found inshore ..................................................... 57
3.3
Conservation needs of the wider pelagic environment of the tropical Atlantic .......... 59
4.
Conclusions ................................................................................................................ 61
4.1
Sources, quality and extent of information ............................................................... 61
4.2
The marine biodiversity importance of Ascension’s offshore waters ........................ 61
4.3
The main threats to maintaining and enhancing the offshore marine biodiversity .... 62
4.4
What would a no-take MPA protect and secure? ..................................................... 62
4.5
What are the main data gaps to fill? ........................................................................ 63
5.
References ................................................................................................................. 64
6.
Bibliography ................................................................................................................ 72
Appendix: Species of ‘game fishes’ and ‘deep water fishes’
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The Offshore Marine Environment of Ascension Island, South Atlantic
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The Offshore Marine Environment of Ascension Island, South Atlantic
Executive summary
1

The waters surrounding Ascension Island, extending to the 200 nautical mile (370 km) limit of the
Exclusive Economic Zone (EEZ) (an area of 445,390 km2), are currently being proposed (by the
RSPB and others) as a large-scale Marine Protected Area, where no extractive activities
(particularly commercial fishing) would be permitted. However, the proposal includes a recreational
and sport fishing zone extending from 0 – 12 nautical miles (22 km) around the island (forming an
2
area of approximately 2,400 km ), where local fishing activity would be permitted. If implemented
as proposed, the outer, fully protected ‘Ocean Sanctuary’ would cover approximately 443,000 km2
of ocean surrounding the island.

Relatively little is known about the marine life which inhabits the surface waters, the mid-depths
and the ocean floor of this vast area, on account of the paucity of research which has been
conducted around Ascension over the years. Most research has been undertaken on key species
of conservation concern such as turtles and seabirds. Information on commercial fish species is
poor, largely reliant on data from catch landings as well as on-board observers on fishing vessels.
Considerably more is known about the inshore area than further offshore, particularly following a
recent Darwin Initiative project which has been investigating shallow water biodiversity (Brickle et
al., 2013). Overall, levels of scientific knowledge are very similar to the amount of information
available for the UK Overseas Territory of the Pitcairn Islands.

The Ascension Island EEZ is on the southern edge of the main fishing grounds for bigeye tuna.
This is the primary target species of a commercial longline fishery, mainly undertaken by
Taiwanese and Japanese vessels. Yellowfin tuna, swordfish, blue marlin and sailfish (as well as
other species) are also taken, though in smaller quantities. Recent stock assessments for the
ICCAT region (that is, the whole of the Atlantic Ocean, the Mediterranean Sea, the Black Sea and
the Baltic Sea) indicate that catches of bigeye tuna and swordfish are considered sustainable1
(within the fishery as a whole), and probably those of yellowfin tuna too (Reeves & Laptikhovsky,
2014). However, it is apparent that regional stocks of blue marlin and sailfish are currently being
over-fished (Reeves & Laptikhovsky, 2014). Specific stock assessments of Ascension tuna and
billfish populations have not been carried out.

The greatest cause of conservation concern relating to the fishery is the number of sharks that are
being caught as bycatch, particularly the blue shark whose conservation status is nearthreatened. Incidental catch rates of seabirds, turtles and cetaceans are considered to be ‘very
low’, but still take place. From research published in 2009, based on observations made on board
Taiwanese tuna longline vessels whose area of operation included Ascension’s waters between
2002 to 2006, 35% of the total tuna catch consisted of bycatch fish species, most notably blue
sharks (52%), other shark species (11%) and other fish species (37%). For the period from 2011 to
2013, the bycatch of blue sharks caught from the Ascension ‘area’ (larger than just the EEZ)
amounted to an average of 463 tonnes/year.

Ascension is the largest nesting site for endangered green turtles in the South Atlantic. Every 3-4
years, these turtles leave their feeding grounds off the coast of Brazil to travel to Ascension to
breed, a distance of 2300 km. Numbers of nests on the island’s sandy beaches have been steadily
increasing since a ban on commercial harvesting was introduced 70 years ago, together with legal
protection. Since monitoring of nest sites began in 1977, the average number of green turtle
clutches deposited annually has increased six-fold, from 3,700 to 23,700 (Weber et al., 2014). At
Note that the term ‘sustainable’ is used here in a commercial fishery sense only, whereas current populations of
these species are likely to have declined considerably from their naturally occurring, pre-commercial fishing
population sizes.
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The Offshore Marine Environment of Ascension Island, South Atlantic
the end of the nesting season, adults migrate back to Brazil. With effective protection and
monitoring in place at Ascension, the main threat to these turtles is now considered to be from
fishing gear closer to the Brazilian coast.

Ascension Island is one of the world’s most important tropical seabird breeding sites and the
most important in the tropical Atlantic. In addition to the island’s own endemic species of
frigatebird, there are 10 other seabird species which breed around the island’s fringes, numbering
2
in excess of 400,000 individuals , with many concentrated on the offshore stack of Boatswainbird
Island. Several of these species, fitted with tracking devices, have been found to forage over
hundreds of kilometers of ocean. The endemic Ascension frigatebird, whose conservation status is
Vulnerable, spends much of its time at sea, with individuals being found to venture as far as the
coast of West Africa.

A total of 5 species of cetacean have been recorded from within Ascension Island’s EEZ. This is
probably an underestimate of the true figure, as most sightings have come from the island’s
nearshore waters where there is greater boat/ship traffic and more opportunity to make sightings.
A small group of humpback whales visit the island each year around September/October and
though they have young with them, it is unclear whether they use the island’s waters as a calving
and breeding area. It is postulated that they would have migrated from the cool waters of the
Falklands or even the Antarctic.

12 species of shark have been recorded from within the EEZ, together with giant manta ray and
the smaller devil ray. Of the shark species, the scalloped hammerhead is regarded worldwide as
being endangered. In parts of the Atlantic Ocean, scalloped hammerhead populations have
declined by over 95% in the past 30 years on account of it being targeted by commercial fishing
operators for its highly prized fins.
Galapagos sharks are the most frequently encountered shark species in the island’s nearshore
waters and they are occasionally taken by local sports fishing vessels. Populations of this shark at
other sites within its range have come under pressure from targeted fishing, bycatch by
commercial longline operators and the species’ slow reproductive rate. News of their total
extinction (believed to have been a result of overfishing - see Luiz & Edwards, 2011) from St Paul’s
Rocks, a small archipelago of barren islets lying to the north-west of Ascension on the Mid-Atlantic
Ridge, where they were once very numerous, makes for a salient lesson in the management of
these apex predators in the waters surrounding remote, offshore islands and seamounts.
2

Within the extent of the EEZ are three distinct seamounts which rise to between 316 m and 70 m
of the surface. These undersea mountains can provide great insights into patterns of marine
biodiversity. They may vary greatly in their biodiversity, can have a high degree of endemism, may
be centers of speciation, and may act as "stepping stones" for the dispersal of coastal species.
The three within the Ascension Island EEZ have been little studied, although recent video footage
by National Geographic from a deep-water ROV deployed on the Grattan seamount
(approximately 250 km to the south-east of Ascension) has confirmed the presence of a number of
fish species which were thought endemic to Ascension and/or St Helena.

Very little information exists on the EEZ’s deep sea benthos (i.e. marine life living on the seabed
below 100 m depth) which is largely unstudied and a major gap in knowledge. A total of just 26
species of ‘deep water fishes’ are listed as occurring at Ascension.

Several of Ascension’s seabird species rely, indirectly, on the presence and behaviour of tuna (and
other large fish species) in order to catch their prey (Au & Pitman, 1988). Tuna species, particularly
Note, however, that once the island’s seabird populations were considerably larger than present day populations,
with declines probably being caused by human and cat predation (now both stopped), and, more arguably, by the
diminution of prey availability caused by the depletion of large fish (tuna and billfish, in particular) by the fishing
industry.
iv
The Offshore Marine Environment of Ascension Island, South Atlantic
yellowfin Thunnus albacares, in pursuance of their own prey, tend to drive smaller pelagic fish to
the surface. In the case of flyingfish, they are likely to glide above the surface of the sea during
these chases in order to escape being caught by the tuna. Flyingfish form the principal diet of both
boobies and frigatebirds, which they obtain near or above the sea surface (Oppel et al., 2015).
Sooty terns are also reliant upon large schools of surface-swimming tuna to drive their prey within
reach (Au & Pitman, 1988). Thus, in order to maintain healthy populations of these seabirds, there
is heavy reliance on the presence of tuna schools within their foraging ranges.

At present, there are no large-scale, benthic or pelagic reference areas (i.e. areas where
extractive human activities have been banned, allowing the enclosed ecosystems to function
entirely naturally) anywhere in the tropical Atlantic. The UK has led the way in promoting such
scientific reference areas further south in the Atlantic at South Orkney in 2009 and along the length
of the Antarctic peninsula in 2012. The creation of a MPA at Ascension would provide such a
reference area, a major sanctuary of global significance in an ocean where a considerable number
of apex predators such as tuna, billfish and sharks are removed by commercial fishing operators.
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The Offshore Marine Environment of Ascension Island, South Atlantic
Abbreviations & explanations of terms used in the text
AIG
Ascension Island Government
bathy-pelagic
The bathyal zone, part of the pelagic zone that extends from a depth of 1000 m to
4000 m below the ocean surface. It lies between the meso-pelagic above, and the
abysso-pelagic below.
CITES
Convention on International Trade in Endangered Species of Wild Fauna and Flora
CMS
Convention on the Conservation of Migratory Species of Wild Animals
EEZ
Exclusive Economic Zone (formerly Exclusive Fisheries Zone, EFZ). Extends out to
200 nm (370 km) from the island’s coastline.
ICCAT
International Commission for the Conservation of Atlantic Tuna, the Regional
Fisheries Management Organisation responsible for the conservation and
management of tuna and tuna-like species in the Atlantic.
IUCN
International Union for the Conservation of Nature
IUU
Illegal, Unreported and Unregulated fishing
longline
A type of fishing gear in which individual baited hooks on short branch lines are
attached to long main lines. They can be fished at or near the surface, as is the
case in the Atlantic tuna fishery, or on the sea bottom.
meso-pelagic
Also known as the twilight zone, the meso-pelagic is that part of the pelagic zone
that extends from a depth of 200 to 1000 metres below the ocean surface.
MPA
Marine Protected Area
pelagic
Living in the water column, i.e. away from the bottom, and frequently near the
surface.
ROV
Remote Operated Vehicle
RSPB
Royal Society for the Protection of Birds, a UK charitable Non-Governmental
Organisation (NGO)
seamount
An underwater mountain rising from the ocean seafloor that does not reach to the
water's surface (sea level), and thus is not an island. Seamounts are typically
formed from volcanic activity.
UK
United Kingdom of Great Britain and Northern Ireland
UNCLOS
United Nations Convention on the Law of the Sea
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The Offshore Marine Environment of Ascension Island, South Atlantic
1.
Introduction
At 7° 57′ S, 14° 22′ W, Ascension Island lies almost midway between the continents of South America
and Africa in the South Atlantic Ocean. The nearest land to Ascension is the similarly diminutive island
of St Helena which lies some 1100 km to the south east (Fig. 1). Ascension, therefore, has the peculiar
distinction of being one of the most remote islands in the world. It is part of the United Kingdom
Overseas Territory of St Helena, Ascension and Tristan da Cunha.
The island of Ascension exists as the visible pinnacle of a massive submarine volcano which erupted
from the Mid-Atlantic Ridge some one and a half million years ago. It now lies approximately 145 km to
the west of the Ridge, 1500 km from the coast of West Africa to the north east, and 2300 km from the
coast of Brazil which lies due west. Much of the island’s surface is still pock-marked by volcanic peaks,
craters and vast flows of unvegetated lava, solidified into extremely hard rock formations. Although
there have been no eruptions since the island was permanently inhabited in 1815, physical textures
suggest that the most recent deposits erupted less than 500 years ago (Faneros & Arnold, 2003).
Fig. 1. Map showing the location of Ascension Island in the South Atlantic Ocean. The
200 nm EEZ is shown in red.
1.1
Ascension Island - geographical context
The island is almost triangular in outline, being 14 km across from east to west and 11.2 km from north
to south. Its land area of 97 km2 is entirely volcanic in origin, with much of it, particularly to the north and
the east, remaining as bare rock outcrops with massive lava flows and ash cones (Figs. 2 & 3). The
highest point of the island is the peak of Green Mountain which stands at 859 m above sea level. The
coastline varies from dramatic 200 m high cliffs at the south-east corner, to gently shelving sandy bays
along the west coast, separated by a multitude of small knobbly headlands and rock outcrops.
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The Offshore Marine Environment of Ascension Island, South Atlantic
Fig. 2. Satellite view of Ascension Island.
Satellite Image (c) Space Imaging.
1.2
Fig. 3. Map of Ascension. Note the presence of
Boatswainbird Island, the larger of the two ‘stacks’
close to the eastern promontory.
Ascension’s nearshore marine biodiversity
Ascension’s marine life is poorly studied. Much more information is known about the shallow sublittoral
zone around the island than is known about the deeper, offshore waters. Scuba surveys have
documented the dominant sublittoral substrata to be of volcanic rock and sand (AIG, 2014). Underwater
rock formations consist of bedrock reefs, vertical cliffs and steep boulder slopes, as well as a variety of
caves, canyons and lava tubes. There are also gently shelving areas of coarse sand and maerl
cobbles, particularly on the western side of the island, though their inherent instability means they
support a depauperate, albeit distinctive, animal and plant community (AIG, 2014).
Unlike most tropical islands, Ascension has no coral reefs. Instead, the nearshore marine life is
characterised by an abundance of fish, a largely cryptic and nocturnal invertebrate fauna, and a striking
scarcity of erect, benthic macroalgae (Irving, 2013). Rock surfaces are frequently covered by encrusting
and erect calcareous red algae (Lithothamnia sp.). These appear to be the only forms of seaweed
which can survive the attention of the large numbers of grazing fish and sea urchins (Irving, 1989). Over
100 species of seaweed have been recorded from the shallow sublittoral (Price & John, 1980; Tsiamis
et al., 2014) but these, together with a variety of sessile invertebrates, are often hidden away in
crevices inaccessible to grazing organisms.
Although abundant, fish diversity is low when compared to other tropical Atlantic islands. A total of 133
‘coastal’ fish species have been recorded in Ascension waters, representing a unique assemblage of
western, eastern and amphi-Atlantic species (Wirtz et al., 2014). The fish fauna is dominated by very
large numbers of the black triggerfish Melichthys niger. Large pelagic fish such as yellowfin tuna
Thunnus albacares, rainbow runner Elagatis bipinnulata and Galapagos shark Carcharhinus
galapagensis also venture into the shallow sublittoral zone to feed on inshore species such as
Melichthys niger (AIG, 2014).
There is a UK Darwin Initiative project currently underway entitled the Ascension Island Marine
Sustainability (AIMS) project. The project aims to increase Ascension Island’s marine biodiversity
knowledge and fisheries science capacity substantially, informing the development of the Biodiversity
Action Plan for marine taxa, and providing the science base needed for sustainably managed inshore
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The Offshore Marine Environment of Ascension Island, South Atlantic
and offshore fisheries (AIG website, 2015). The project is being carried out with primary partners at
SAERI (the South Atlantic Environment Research Institute based in the Falklands), and with input from
RSPB (Royal Society for the Protection of Birds), BAS (British Antarctic Survey) and SMSG (Shallow
Marine Survey Group). This project follows another Darwin-funded project in 2012 which assessed the
nearshore marine biodiversity and initiated inventories of invertebrates, the fish fauna and algae
(http://www.smsg-falklands.org/blog/2012/06/15/marine-biodiversity-survey-of-ascension-island).
Water temperature in the shallow sublittoral is relatively warm and stable, ranging between
approximately 22-24 ° C in September/October and 28-29 ° C in March/April (AIG Conservation,
unpublished data). Tidal range is small (0.8m) and average wave height does not exceed 2m. Few
areas could be regarded as even moderately sheltered, although wave and current action is strongest
along southern and eastern shores exposed to the prevailing south-easterly trade winds. The trade
winds and westward flowing surface currents have a pervasive effect on the oceanography of the
shallow sublittoral zone, with a clear east-west gradient in temperature and salinity (AIG, 2014).
1.3
Island governance and history
The three island UK Overseas Territories of Ascension, St Helena and Tristan da Cuhna are overseen
by a Governor (based in St Helena), although Ascension has its own island-based Administrator.
Officially there are no permanent residents living on the island: all personnel are ‘temporary’ (although
depending on their contracts they may in practice remain on the island for many years) and are either
employed or are spouses or partners of employees. The main employers on the island are the
Ascension Island Government (AIG), the Royal Air Force (RAF), the United States Air Force (USAF)
(responsible for building the island’s airstrip during WWII), the British Broadcasting Corporation (BBC)
and the Composite Signals Organisation (CSO), amongst others. An elected Island Council advises the
Governor on laws, policies and the government’s annual budget. The UK Government remains
responsible for Ascension Island’s external relations, defence and internal security. Since April 2002 the
island’s revenue has derived from locally raised taxes, import duties, the sale of philatelic stamps and
(from October 2010 to December 2013) the sale of fishing licences.
The island was discovered by the Portuguese ‘empire builder’ Afonse du Alberquerque in 1503 on
Ascension Day. Being dry and barren it was of little use to the East Indies fleets. So it remained
uninhabited until Emperor Napoleon I was incarcerated on St Helena in 1815 when a small British naval
garrison was stationed on Ascension to deny it to the French. The island was designated “HMS
Ascension”, a “Stone sloop of War of the smaller class” (http://www.ascension-island.gov.ac/theisland/history). By Napoleon’s death in 1821 Ascension had become a victualling station and
sanatorium for ships engaged in the suppression of the slave trade around the West African coast. In
1823 the island was taken over by the Royal Marines. It remained under the supervision of the British
Board of Admiralty until 1922, when it was made a Dependency of St Helena.
AIG’s Conservation Department is responsible for the management of the island’s waters, extending to
the limit of the EEZ. Despite the UK Government having certain on-island responsibilities, the island’s
waters are not included within the geographical remit of the European Union’s Common Fisheries
Policy. The island, similar to other UK Overseas Territories, has its own distinct fisheries management
regime (Appleby, 2015). The Wildlife Protection Ordinance was recently updated in October 2013 “to
protect and preserve the wildlife and habitat of Ascension” (AIG website, 2015), and covers marine
species and habitats too. The Ordinance confirms that Fishing Limits extend to the limit of the island’s
territorial waters (i.e. 200 nm or 370 km); that Prohibited Areas and/or Closed Seasons may be
established to protect particular species; and that there is a list of named species (“wildlife products”)
which are protected by the Ordinance (see Table 1 below).
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The Offshore Marine Environment of Ascension Island, South Atlantic
Table 1. Schedule of “wildlife products” as listed in the Wildlife Protection Ordinance, 2013.
Reptiles
Green turtle
Hawksbill turtle
Birds
Ascension Island frigate bird
Masked booby
Brown booby
Red- footed booby
Sooty tern (aka Wideawake
tern)
Fairy tern (aka White tern)
Chelonia mydas
Eretmochelys imbricata
Fregata aquila
Sula dactylatra
Sula leucogaster
Sula sula
Onychoprion fuscatus
Gygis alba
Black noddy
Brown noddy
Red- billed tropic bird
Yellow- billed tropic bird
Anous minutus
Anous stolidus
Phaethon aethereus
Phaethon lepturus
Storm petrels
Oceanodroma spp.
Mammals
Bottlenose dolphin
Fish
Whale shark
Manta rays
Ascension scorpionfish
Resplendent angelfish
Ascension hawkfish
Lubbock’s gregory (aka
Yellowtail damselfish)
St Helena wrasse
Ascension wrasse
Ascension goby
St Helena butterflyfish
Bicolour
butterflyfish
(aka
hedgehog
butterflyfish)
St Helena sharpnose
pufferfish
Marmalade razorfish
Tursiops truncatus
Rhincodon typus
Manta spp.
Scorpaena ascensionis
Centropyge resplendens
Amblycirrhitus earnshawi
Stegastes lubbocki
Thalassoma
sanctaehelenae
Thalassoma ascensionis
Priolepis ascensionis
Chaetodon sanctaehelenae
Prognathodes dichrous
Canthigaster
sanctaehelenae
Xyrichtys blanchard
Various highly migratory species which occur within the island’s EEZ, such as Atlantic sailfish, albacore
and yellowfin tuna, are included within Annex I of the 1982 United Nations Convention on the Law of
the Sea (UNCLOS). St Helena and its Dependencies (via the UK) are signatories to the Convention on
International Trade in Endangered Species of Wild Fauna and Flora (CITES) and the Convention on the
Conservation of Migratory Species of Wild Animals (CMS).
Much of Ascension Island, as well as Boatswainbird Island (a seabird-dominated rock off the main
island’s east coast – see Fig. 3), are currently designated as Important Bird Areas by Birdlife
International.
The island’s own National Protected Areas Regulations 2014 provide for the establishment of protected
areas, the protection of named species within these areas, and the restriction of all forms of
development within these areas. The regulations also prohibit access to Boatswain Bird Island without a
permit.
1.4
Proposals for a Marine Protected Area
3
The RSPB has been working to establish a large Marine Protected Area (MPA) around Ascension
Island, extending out to the limit of the EEZ, since 2013. Declaration of such an MPA would be by the
Governor. In their manifesto commitments for the general election in May 2015, the UK Conservative
Party (who subsequently won the election) stated that “we will designate a further marine protected
area at Ascension Island, subject to the views of the local community”. In 2010, the UK Government
declared a very large MPA around the Chagos archipelago in the Indian Ocean (another UK Overseas
Territory) (Sheppard et al., 2012), and has recently declared its intention to establish an MPA around
the Pitcairn Islands in the South Pacific (Dawson, 2015), covering an area of 835,000 km2.
3
The term ‘Marine Protected Area’ can be interpreted in various ways. In the context used here, essentially, it
would mean the prohibition of extractive activities within 12 nm to 200 nm of the island.
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The Offshore Marine Environment of Ascension Island, South Atlantic
The RSPB (2014) believes that the creation of a large scale, fully protected no-take MPA extending
from 12 nm to 200 nm offshore (the extent of Ascension’s Exclusive Economic Zone) – an area of over
443,000km2 - represents “the best opportunity to protect the biodiversity of Ascension’s waters and
contribute to the conservation of the pelagic ecosystem of the tropical Atlantic”. Sport fishing activities
would be permitted to continue within an inner area (approximately 2,400 km2), extending from the
coast to 12 nm offshore.
The RSPB list a number of reasons to support their proposal for a MPA around Ascension (J. Hall,
pers. comm.):

It is one of the most important tropical seabird islands in the world, where RSPB removed feral
cats over ten years ago.

RSPB has been working in partnership with the Ascension Conservation Department ever since,
and were extremely concerned by the poorly managed Taiwanese long-lining fishery which was
opened in Ascension’s waters in 2010.

RSPB believe that marine protection builds upon their historic seabird conservation agenda and
offers the best future opportunity for Ascension’s community and marine environment.

Ascension lies in productive waters and so has a high biodiversity value marine environment
worthy of protection, not just for seabirds and the megafauna which remains (such as very large
blue marlin), but also to enable the recovery of species such as sharks, which are widely reported
on-island to have been greatly reduced or to have disappeared almost entirely.

Finally, Ascension represents one of the only places in the tropical Atlantic where ecosystem-scale
protection is possible, due to the paucity of EEZs in this region.
The island currently has no specific marine protected areas, although approximately 0.45 km2 of sandy,
sublittoral habitat adjacent to major sea turtle nesting beaches are included in Nature Reserves
designated under the National Protected Areas Order 2014 and National Protected Areas Regulations
2014. These are primarily intended to protect the mating and inter-nesting habitat of the internationally
important green turtle population, with restrictions on development and access by certain types of water
craft (AIG, 2015a).
1.5.
1.5.1
The scope of this report
The purpose of the study
This report has been commissioned by the RSPB with the following purpose:
To complete a scientific review and conservation status assessment of the offshore marine
environment (12 nm – 200 nm) around the UK Overseas Territory of Ascension Island in order to
inform scientifically rigorous conservation management. To collate all known scientific information
about the offshore marine environment into one report, highlighting species richness, known
population trends, and existing or potential future threats. Given the limited data available, it is
envisaged that information and inferences will need to be drawn from research conducted within
both Ascension’s nearshore environment and the regional high seas, or other best available
evidence and proxies as appropriate. It will use this information to evaluate the conservation needs
of Ascension’s marine environment.
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The Offshore Marine Environment of Ascension Island, South Atlantic
1.5.2
Methodology used
The study has been purely desk-based with no visit to the island. However, e-mail communication with
members of staff of the AIG Conservation Department (Dr Nicola Weber and Dr Judith Brown) has
been most informative and helpful. The author has had access to their database of scientific literature
relating to the island’s marine environment, which has proved a most useful starting point. Further
reference material has come from the RSPB’s own digital ‘Ascension library’. In addition to these
sources, specific papers have been tracked down via the internet. The author visited Ascension 30
years ago as a member of a 5-week long diving expedition to the island.
A comprehensive bibliography of scientific papers relevant to the offshore environment has been
compiled, which is included as Section 6 to this report.
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The Offshore Marine Environment of Ascension Island, South Atlantic
2. Collation of scientific knowledge
For the purposes of this review, information has been gathered from a variety of sources, most
particularly scientific papers and reliable internet sites. When used, these sources have been
acknowledged in the text and listed under References (section 4). There is also a much larger
Bibliography (section 5), which includes all references which have been sourced for possible use for
this review. These have been arranged by subject.
2.1
2.1.1
An overview of the geophysical and oceanographic context
Geophysical context
Understanding the formation of the ocean floor
The Atlantic Ocean is the Earth’s youngest ocean. It has been formed by the separation of the
continents of the Americas and those of Africa and Eurasia. The Mid-Atlantic Ridge is located at the
juncture of crustal plates that form the floor of the Atlantic Ocean. It is considered a "slow-spreading"
ridge (the ridges in the Pacific are faster-spreading), at a rate estimated to be approximately 1-5 cm/yr.
Running along the crest of the ridge is a long rift valley that is about 80 to 120 km wide. This contains
the zone of seafloor spreading, in which molten magma from beneath the Earth’s crust continuously
wells up, cools, and is progressively pushed away from the ridge’s flanks (Fig. 4).
Fig. 4. A topographic section of the Mid-Atlantic Ridge. The high flanks on both sides of the rift valley
are shown in red. The highest areas are red and the lowest areas are blue. The rift valley is a linear
low-lying area between the flanks of the ridge. A Fracture Zone, running at right-angles to the Ridge, is
visible at the top of the image. The large features are covered with smaller-scale features that might be
considered "texture". Image: Kenneth C. Macdonald & Paul J. Fox (UCSB).
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The Offshore Marine Environment of Ascension Island, South Atlantic
Although this seafloor spreading process occurs steadily over geologic time (tens or hundreds of
thousands of years), on a day-to-day basis the formation of oceanic crust happens in fits and starts small earthquakes occur as the plates break while pulling apart; some blocks of rocks are pushed up
and some drop down; magma is squeezed through the fractures in the rocks and may extrude on the
seafloor to form small volcanic cones; and time may pass with very little noticeable change in the
landscape (http://earthguide.ucsd.edu/mar/intro2.html). The spreading centres themselves form broad
central ridges that sink steadily with age and distance, starting at about 2,500 m water depth and
sinking to typical open ocean depths of 4,000 meters. This unevenness of spreading and plate creation
usually produces volcanic ridges and fault-bounded hills that may rise up several hundred metres
above the surrounding seafloor.
A major 240 km offset of the rift valley is made by the Ascension Fracture Zone, some 50 km north-east
of the actual island of Ascension (van Andel et al., 1973). It is possible to trace this Fracture Zone
topographically from the Pernambuco Abyssal Plain in the west, across the Mid-Atlantic Ridge, and
along most of the Guinea Ridge to the east, a total length of 4400 km (see Fig. 14 in section 2.9). The
rift valley just south of the Ascension Fracture Zone reaches depths of 3600 m, remains uncut by
offsets for at least 50 km and is bordered by several parallel ridges on either side (Faneros & Arnold,
2003). In geomorphological terms, the island is an intra-plate volcanic island and is located 90 km west
of the Mid-Atlantic Ridge (Fig 5). However, the above sea portion of the island accounts for less than
1% of the volcano’s total volume (Nielson & Sibbett, 1996), with the 60 km basal diameter lying in
3,200 m depth of water.
Seismic activity still continues near the Ascension volcano, being concentrated on the Mid-Atlantic
Ridge and the Ascension Fracture Zone. Minor earthquakes occur nearly every other day though all are
centered outside the Ascension volcano. A study by Hansen et al. (1996) recorded a range of
earthquake magnitudes from 0.4 to 4.2. They were shallow events, with hypocentres ranging in depth
from 500m to 2500m.
2.1.2
Oceanographic context
The Mid-Atlantic Ridge divides the Atlantic Ocean longitudinally into two halves. Its presence has a
major influence on the circulation of near-bottom water masses (Tomczak and Godfrey, 1994). Deep
Fracture Zones (such as the Ascension Fracture Zone) which run at right-angles to the Ridge, provide
routes for bottom water to pass from one side of the ocean to the other (Levin & Gooday, 2003).
The main current which affects Ascension, for the most part, is the South Equatorial Current (Fig. 6).
This flows close to the surface from east to west and, along the Equator, may reach speeds in excess
of 1 m/s. However, the island is also affected from time to time by the usually deeper-flowing (and
colder) Atlantic Equatorial Undercurrent (also known as the Southern Equatorial Counter-Current),
which flows from west to east. The interaction of these two currents can give rise to localised
turbulence, gyres and eddies which combine with upwellings in nearshore waters caused by the seabed
topography, giving rise to considerable mixing of the water types in the vicinity of Ascension (AIG,
2012). This mixing is responsible for the higher levels of productivity around the island than one might
expect to see in otherwise typically oligotrophic waters.
Close to the ocean floor, the water is never still, because tidal forces move water at all ocean depths.
As a result, the water bathing all sessile sea-bed organisms slowly changes, bringing food and
removing wastes. These ocean floor currents are not uniform however, and their dynamics will change
with the presence of localised features such as canyons, abyssal hills and seamounts.
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The Offshore Marine Environment of Ascension Island, South Atlantic
Fig. 5. 3D bathymetric views and a plan view (lower left), showing the distinctive nature of the
Ascension volcano (marked ‘AI’) arising from the deep ocean floor surrounding it, and its
relationship to the Mid-Atlantic Ridge (MAR). Taken from the Recommendations of the Commission on
the Limits of the Continental Shelf in regard to the Submission made by the United Kingdom of Great Britain
and Northern Ireland in respect of Ascension Island on 9 May 2008.
Fig. 6. Generalized circulation map depicting the major currents in the Atlantic. NAG, North Atlantic
Gyre; AEU, Atlantic Equatorial Undercurrent; SAG, South Atlantic Gyre; CAR, Caribbean Current;
GS,Gulf Stream; CC, Canary Current; GC, Guinea Current; NEC, North Equatorial Current; SEC,
South Equatorial Current; BR, BrazilCurrent; BEN, Benguela Current. (After Muss et al., 2001).
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The Offshore Marine Environment of Ascension Island, South Atlantic
2.1.3
Ocean floor habitats
The deep Atlantic Ocean floor is covered by sediments deposited by volcanic processes, by turbidity
currents and related gravity-driven processes, by bottom currents and by pelagic sedimentation (Emery
& Uchupi, 1984). Sediments become progressively finer with increasing depth and distance from land,
with deposition rates being higher in the central parts of the Atlantic. Over much (67%) of the Atlantic
Ocean, the surface sediments are carbonate oozes (CaCO3 content 30–50%) (as opposed to siliceous
oozes, more prevalent closer to the polar regions), with a mean particle size of <100 mm; a sand-sized
fraction consisting predominantly of planktonic foraminiferan tests; and an organic-carbon content
generally <0.5% (Emery & Uchupi, 1984).
Sediment primarily accumulates in local depressions along the steep, rugged Mid-Atlantic Ridge terrain.
Seafloor sediments thicken away from the Mid-Atlantic Ridge, with those near the Ascension volcano
ranging from 250 m to 340 m thick. They continue to thicken to the west and, within the Ascension
Fracture Zone, may accumulate to being as much as 530 m thick locally (Faneros & Arnold, 2003).
At a more local level, the surface of the sedimentary ooze will display signs of animal life with features
such as pits, burrows, mounds, tracks, fecal casts and resting traces. Many of these result from
movement, burrowing, feeding, defecation or dwelling/construction by benthic invertebrates and fishes.
Such traces of animal activity (or lebensspuren, as they are known) often provide the main evidence for
the presence of large organisms on abyssal plains and elsewhere in the deep sea, and may be
particularly useful for quantifying buried mega-infauna (i.e. large animals living within the sediments).
These organisms, which are very difficult to sample using conventional methods, potentially play a
major role in deep-sea community ecology and in the structuring of the deep-sea sedimentary
environment (Faneros & Arnold, 2003).
2.1.4
Physical conditions on the ocean floor
Whilst the deep-sea floor is an extreme environment, it is also a physically stable environment. At
depths below about 800 m, water temperature remains remarkably constant, at about 2°C on the
abyssal plain. These cold temperatures reduce chemical reaction rates and have a bearing on the pace
of life on the sea floor. Pressure increases by 1 atmosphere for every 10 m of depth. Pressure can
affect deep sea organisms physiologically (high deep sea pressures oppose the secretion of gas) and
biochemically (because the performance of proteins (e.g. enzymes) and lipids (e.g. cell membranes)
changes with pressure). Salinity at these depths is likely to be ‘normal’ for seawater, i.e. at about 35
parts per thousand. Dissolved oxygen is carried to the deep-sea floor by the descent of surface waters.
The water overlying most of the deep-sea floor is saturated with oxygen or nearly so (5–6 ml/l) and so is
not a limiting factor for the majority of organisms. Certain conditions though will reduce oxygen
concentration to levels that are problematic for organisms (Thistle, 2003). One occurring within the
Ascension EEZ is likely to be organic material (e.g., faecal pellets) falling from the euphotic zone, being
decomposed by aerobic bacteria and then consumed by zooplankton as it sinks. This will contribute to
an oxygen sink in the mid-water zone. Where ocean floor currents are locally enhanced, eddies can
develop and sediment resuspension is likely to occur. These episodic events, termed ‘abyssal
storms’, can erode and re-deposit several centimeters of sediment within a short period.
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The Offshore Marine Environment of Ascension Island, South Atlantic
The following sections (2.2. to 2.8) set out what is known about the marine life which inhabits the
offshore waters around Ascension Island – commercial fish species, non-commercial fish species,
sharks and rays, cetaceans, turtles, seabirds, and molluscs and other invertebrates. Wherever possible,
a description is given of the known range of a species, its population size worldwide (and whether this
is increasing or decreasing), its conservation status and any threats it might face. Further information is
then given, where known, with regard to its status within the Ascension Island EEZ.
2.2
Commercial fish species
The species of fish which occur within Ascension’s EEZ can be divided into two groups: migratory and
resident. Resident species tend to be found in the shallower waters close inshore. Of a total fish fauna
of 173 species, Wirtz et al. (2014) list 133 as being ‘coastal’ species. These species spawn and recruit
locally with populations rarely being supplemented by fish migrating from more remote stocks
(Armstrong & Reeves, 2015). Migratory species, on the other hand, are likely to originate from
spawning and recruitment beyond the 200 nm EEZ. Large pelagic species that are migratory and of
commercial interest include various tuna (bigeye and yellowfin in particular) and billfish (particularly
swordfish, though also sailfish and blue marlin). Other migratory species more likely to be caught by
sports fishermen include wahoo, rainbow runner and dolphinfish.
Bigeye tuna is the main target species for commercial fishing fleets operating in the mid-Atlantic,
utilising longlines. It would appear from data reported to the International Commission for the
Conservation of Atlantic Tuna (ICCAT) on catch rates per area that the Ascension EEZ is on the
southern and western edges of the main fishing grounds for bigeye tuna. Most fishing activity is towards
the edge of the EEZ, particularly in the northern part, but there is marked seasonal and annual variation
in this (Reeves & Laptikhovsky, 2014). The fishery in the Ascension EEZ is highly seasonal, with the
highest catches over December-January and negligible catches over July-September (Reeves &
Laptikhovsky, 2014).
Table 2 lists ten species of fish which are known to be of commercial interest and which are known to
occur within the Ascension EEZ. The following brief descriptions are given for those species of
conservation concern (i.e. they are Endangered or Near Threatened) or which are mainly targeted by
commercial fisheries.
Bigeye tuna Thunnus obesus
Bigeye tuna can grow up to 2.5 m in length and weigh up to
180 kg. The species is distributed throughout the Atlantic Ocean
between 50°N and 45°S. It tends to be found in greatest numbers
where the water temperature is between 17° and 22°C (Froese &
Pauly, 2015). Variation in occurrence is closely related to seasonal and climatic changes in surface
temperature and thermocline. Bigeye tend to swim deeper than other tuna species and show
substantial vertical movements in the water column (Reeves & Laptikhovsky, 2014), descending into
deeper water at daybreak and returning to surface waters at dusk. The IUCN Red List status for Bigeye
tuna is ‘Vulnerable’. This is largely due to the fact that there has been an estimated global decline of
42% of the stock over the 15 year period from 1992-2007 (Collette et al., 2011d).
This is the main target species for commercial fishing vessels using longlines within the Ascension
EEZ, accounting for between 74-82% of the total catch. Ascension lies close to the southern and
western edge of the main fishing areas, and only in the peak season of December to January does the
Ascension area become relatively important. The reported 2012 catch from the Ascension EEZ was
1,543 tonnes, which amounts to 2.2% of the total catch from this stock in 2012 (Reeves & Laptikhovsky,
2014).
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Yellowfin tuna Thunnus albacares
The yellowfin is one of the larger tuna species, reaching a
maximum length of 2.2 m and a maximum weight of 180 kg. This
species is found worldwide in tropical and subtropical seas. It is
fast-growing, widely-distributed and highly productive. Within the
Atlantic, tagging data show that trans-Atlantic migrations occur,
and the yellowfin tuna from the entire Atlantic are considered to be part of a single stock (Collette et al.,
2011b). The most recent assessment of this stock in the Atlantic was conducted in 2008 (ICCAT 2009).
This paints a confusing picture: recent trends have differed between the western and eastern Atlantic,
with the overall catches in the west declining by 26% since 2006. In the eastern Atlantic, on the other
hand, catches have increased by 23% since 2006, mainly due to substantial increases in purse seine
effort. The IUCN Red List status for yellowfin tuna is ‘Near Threatened’ (Collette et al., 2011b).
Longline catches of yellowfin tuna from the Ascension EEZ comprise only a small percentage of the
total catch: the reported catch from the EEZ in 2012 was 65 tonnes which compares with a total catch
of 101,866 tonnes (or 0.06%) (Reeves & Laptikhovsky, 2014). This species is also caught by angling
boats from Ascension as part of the recreational fishery (Wirtz et al., 2014). Ascension’s sports fishing
business managers report that yellowfin tuna catches were decreasing over time, but over the last two
years they have increased rapidly over all size ranges, with more large fish being caught in particular.
This pattern was noted by other boat operators and may be related to an overall increase in stock
abundance in the South Atlantic (Armstrong & Reeves, 2015).
Albacore Thunnus alalunga
Albacore is a relatively small temperate species of tuna. It grows
to an average length of 1.4 m and a weight of 60 kg. The
species is present in all oceans, though it is not found close to
the surface between 10 ° N and 10 ° S. This species can be
confused with juvenile bigeye tuna, which also has very long pectoral fins, but with rounded tips. The
IUCN Red List status for albacore has changed from ‘Near Threatened’ in 2011 to ‘Least Concern’ in
2015 (Collette et al., 2011c & 2015). This is despite an estimated 37% decline globally in spawning
stock biomass across all stocks over the past 20 years (1987–2007). In 2010 the stock in the South
Atlantic was considered to be in a “slightly overfished state”, but it is not currently being fished above
maximum sustainable yields (Collette et al., 2011c).
Ascension lies at the northern extent of the albacore’s range in the South Atlantic, so is well outside the
main area for the albacore fishery. Catches within the EEZ were very low: during 2012 they amounted
to just 0.12% of the total catch (Reeves & Laptikhovsky, 2014). Wirtz et al. (2014) comment that
albacore are rarely caught by angling boats, typically during the southern hemisphere winter when
water temperatures are lower.
Atlantic bluefin tuna Thunnus thynnus
Bluefin tuna grow to an average length of 2.5 m and may
weigh over 250 kg. The species’ distribution is restricted to
the wider Atlantic region (including the Mediterranean Sea).
Its population has undergone major declines since the 1960s
due to high fishing pressure. Its range has shown larger contractions (minus 46% since 1960) than any
other pelagic species (Collette et al., 2011a). The IUCN Red List status for Atlantic bluefin tuna is
‘Endangered’, the highest category for any fish species listed in this report. This is largely due to the
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The Offshore Marine Environment of Ascension Island, South Atlantic
most recent Red List assessment (undertaken in 2010) showing global declines in populations, most
noticeable of 51% over the past 39 years of the Eastern Atlantic stock. The Western Atlantic stock has
also shown severe declines in the past and has not yet recovered (Collette et al., 2011a).
This species has been recorded from Ascension (Wirtz et al., 2014), though no information is provided
on where, regarding distance from shore or depth of water. It is not targeted commercially (it is not
listed as a commercially-fished species by Reeves & Laptikhovsky, 2014), although it is possible
individuals may be taken as bycatch on longlines.
Swordfish Xiphias gladius
Swordfish may grow to over 3.0 m in length and weigh over
600 kg. The species is pandemic, being found in the Atlantic,
Indian, and Pacific Oceans in tropical, temperate and
sometimes cold waters. The Atlantic population comprises two stocks that are genetically distinct:
South Atlantic and North Atlantic. The South Atlantic stock has been overfished in the past, but an
assessment of stock levels in 2011 show levels to have stabilized (Collette, 2011e). Worldwide, their
status is considered to be Least Concern.
A total catch of 116.2 tonnes of swordfish was reported by vessels licensed to fish within the EEZ
during 2012. This amounts to 1.14% of the estimated catch from the stock as estimated by ICCAT
(Reeves & Laptikhovsky, 2014). Swordfish is a relatively recent new species to have been caught by
sports anglers at Ascension (Wirtz et al., 2014). Nightime is the best time to catch swordfish.
Sailfish Istiophorus albicans
Sailfish may grow to over 3.0 m in length and weigh up to
58 kg. Wirtz et al. (2014) list the Indo-Pacific sailfish
Istiophorus platypterus as being a previously unrecorded
species for the island. Some authors recognize Istiophorus
platypterus (Shaw 1792) as a single worldwide species (as has been the case historically), while others
now recognize the occurrence of another species of sailfish in the Atlantic, Istiophorus albicans, with I.
platypterus just being present in the Indo-Pacific. In this report, the author has opted for the species
name, I. albicans.
As sailfish favour coastal waters rather than the open oceans they are primarily caught by coastal
artisanal and recreational fishing vessels, with vessels operating longlines further offshore taking them
occasionally as bycatch. Evidence from tagging studies indicates that they move shorter distances than
other billfish species (Reeves & Laptikhovsky, 2014).
ICCAT note concerns about the quality of catch data for sailfish, with substantial problems with underreporting of catches (Reeves & Laptikhovsky, 2014). This problem may also be apparent at Ascension,
with virtually zero catches reported between 1999 and 2011, but then with catches thereafter, including
a reported 21.3 tonnes in April 2013 (Reeves & Laptikhovsky, 2014). It appears as though Ascension
lies on the south-western edge of the main distribution area for sailfish.
Blue marlin Makaira nigricans
The Atlantic blue marlin, which can grow to 5.0 m in length and weigh as much as 650 kg, has a
distribution restricted to the Atlantic Ocean. Interestingly, females may grow up to four times as large as
males. It is considered to be one of Ascension’s iconic species and a sought-after catch for sport
anglers. However, Armstrong & Reeves (2015) reported that the island’s sport fishing business
managers noted that the annual number of blue marlin they have caught was around 120 when they
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The Offshore Marine Environment of Ascension Island, South Atlantic
started fishing in 2000, but in subsequent years has declined
rapidly (112, 73, 34, 20 then 9 per year thereafter). The sport
fishing managers considered that there were 10-year cycles in
peaks in catches, though this has yet to be proven. In March
2013, a British angler visiting Ascension caught the fourth
largest blue marlin specimen ever to have been caught in the
Atlantic, weighing in at 600 kg and measuring 6 m in length –
see photo on right. It would appear that Ascension lies on the
south-western edge of the main distribution of this species.
Commercial vessels licensed to fish within the Ascension EEZ
during 2012 reported a total catch of 11.3 tonnes of blue marlin
(Armstrong & Reeves, 2015).
The record-breaking blue marlin.
th
Metro, 7 March 2013
Other marlin species
Black marlin Istiompax indica is one of the largest marlin
species, growing to 4.5 m and weighing up to 750 kg. It occurs primarily in the tropical Pacific and
Indian Oceans, though a few stray individuals are known to travel around the Cape of Good Hope into
the Atlantic. Although a total catch of 12 tonnes of black marlin was reported from commercial vessels
licensed to fish within the Ascension EEZ during 2012 (Armstrong & Reeves, 2015), there are no
records of black marlin being caught in Ascension waters as yet (Wirtz et al., 2014).
Atlantic white marlin Kajikia albida is caught from time to time around Ascension by recreational anglers
(Wirtz et al., 2014). It is also occasionally caught by commercial vessels from the ICCAT area within
which the Ascension EEZ lies, though because of difficulties with identification (it can be confused with
another species of marlin known as the roundscale spearfish Tetrapturus georgii) total catch data and
stock assessments are uncertain (Armstrong & Reeves, 2015).
Note also that blue shark Prionace glauca and shortfin mako (shark) Isurus oxyrinchus may also be
targeted by certain fisheries interests (see Reeves & Laptikhovsky, 2014, p14).
A search of the on-line FishBase database (www.fishbase.org), using the terms ‘Ascension Island’ and
‘pelagic’, returned ‘0’ results. However, there were returns for the search terms ‘game fish’ and ‘deep
water fish’ (see Table 3, section 2.3).
Further illustrative information on all open water ‘game fish’ species (as listed by FishBase) and all
‘deep sea’ fish species (as listed by FishBase) is provided in the Appendix at the back of this report.
This has been included as readers of this report may be unaware of what many of these fishes look like
and of their worldwide distributions.
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The Offshore Marine Environment of Ascension Island, South Atlantic
Table 2. Species of fishes known to be caught by commercial fishing vessels licensed to fish within the Ascension Island EEZ. (See also Table 13, p 54).
Species
Common name
IUCN Red
List
Reference
Notes
Featured
in
Appendix
Scombridae
Thunnus thynnus
Atlantic bluefin tuna
EN
Wirtz et al., 2014
Very rarely caught at Ascension. Split into eastern (Europe,
Mediterranean & NW Africa) & western (E coast of USA) stocks which
can mix.
Thunnus albacares
Yellowfin tuna
NT
Wirtz et al., 2014; Reeves & According to recent stock assessments, this species is being fished
Laptikhovsky, 2014
sustainably. Catches of this stock within the EEZ constitute a very low
proportion of the total catch (Reeves & Laptikhovsky, 2014).

Thunnus alalunga
Albacore
LC
Wirtz et al., 2014; Reeves & Very rarely caught at Ascension.
Laptikhovsky, 2014

Thunnus obesus
Bigeye tuna
VU
Wirtz et al., 2014; Reeves & Recent stock assessments indicate this species is being fished
Laptikhovsky, 2014
sustainably (Reeves & Laptikhovsky, 2014).

Katsuwonus pelamis
Skipjack tuna
LC
Wirtz et al., 2014
Swordfish
LC
Wirtz et al., 2014; Reeves & Recent stock assessments indicate this species is being fished
Laptikhovsky, 2014
sustainably (Reeves & Laptikhovsky, 2014).
Kajikia albida
Atlantic white marlin
VU
Wirtz et al., 2014; Reeves & Rarely caught at Ascension.
Laptikhovsky, 2014
Makaira nigricans
Blue marlin
VU
Wirtz et al., 2014; Reeves & Indications that this stock is currently being over-fished (Reeves &
Laptikhovsky, 2014
Laptikhovsky, 2014).
Istiophorus albicans
Sailfish
LC
Wirtz et al., 2014; Reeves & Indications that this stock is currently being over-fished (Reeves &
Laptikhovsky, 2014
Laptikhovsky, 2014). Refered to by Wirtz et al. (2014) as I.
platypterus.
Tetrapturus pfluegeri
Longbill spearfish
LC
Wirtz et al., 2014
CR
EN
Fishing pressure “not negatively impacting the population at present”.

Xiphiidae
Xiphias gladius
Istiophoridae
Critically Endangered
Endangered
NT
Near Threatened
VU
Vulnerable
Rarely caught at Ascension.
LC
Least Concern
Page 15 of 115
DD
Data Deficient
NE
Not Evaluated

The Offshore Marine Environment of Ascension Island, South Atlantic
2.3
Non-commercial fish species
‘Non-commercial’ is a broad and rather arbitrary category of dividing up a very large number of fishes
belonging to numerous families. In order to provide some ecological basis for the category, those
species listed in Table 3 have been divided into four groupings:

Species likely to be found on the seabed, in deep water or associated with seamounts;

Species likely to be found in mid-water;

Species likely to be found close to the surface;

Species ‘co-habiting’ with others;
Note that there is a further category of ‘deep water’ fishes which includes those species considered to
be true bathypelagic fishes (i.e. they inhabit the zone between 1000 m – 4000 m deep). These are
included in section 2.10.
The St Helena deepwater scorpionfish Pontinus nigropunctatus was first described from St Helena
(where it was considered endemic), though its range has since been extended to the nearby Bonaparte
seamount (Edwards, 1993), Grattan seamount (Trunov, 2006), St Peter and St Paul Archipelago
(Vaske et al., 2008) and now from Ascension (Wirtz et al., 2014). This extension of a species’
geographical range is likely to be the case for several species, as more exploratory work of the
biodiversity of seamounts takes place in future.
Grattan seamount rises to just 70 m below the surface. It is therefore not surprising to find a number of
species of fishes present close to the plateau on the top of the seamount that are reef fishes rather than
deep water forms. An example of such species is the Bicolour or Hedgehog butterflyfish Prognathodes
dichrous (Fig. 7). Only two butterflyfish species have been recorded from Ascension Island (the other
being the St Helena butterflyfish Chaetodon sanctaehelenae – Fig. 8) and both are also present at St
Helena. Both species are endemic to these two islands, though the former has also now been recorded
from Grattan seamount (see section 2.9).
Fig. 7. Bicolour butterflyfish
Prognathodes dichrous. Photo :
John Taylor, 1985.
Fig. 8. St Helena butterflyfish
Chaetodon sanctaehelenae.
Photo : Robert Irving, 1985.
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The Offshore Marine Environment of Ascension Island, South Atlantic
Aquarists, individuals who keep reef fishes as pets or educators who display them to members of the
public, have a particular affection for butterflyfish as they are often very attractive and make pretty, eyecatching subjects for home and public aquariums. It has been interesting to come across an article on
the internet by an aquarist enthusiast on the fish life of the Grattan seamount. He states, “Indeed, at
least in the context of the aquarium trade, Ascension Island is home to some of the rarest fish species
that are no longer available in the current day. In the old days, Centropyge resplendens [Resplendent
angelfish], Chaetodon sanctaehelenae [St Helena butterflyfish] as well as Prognathodes dichrous
[Bicolour butterflyfish] were the main players coming out of that little mount of sea rock. Endemism is
also high with interesting species such as Priolepis ascensionis [Ascension goby], Amblycirrhitus
earnshawi [Ascension hawkfish] and Xyrichtys sanctaehelenae [Yellow razorfish] just to name a few.”
There is still a demand for endemic species of fishes, taken as live specimens from the wild, with rare
species changing hands for considerable sums of money. Certain species, but by no means all, have
been successfully bred in captivity, which then lessens the need to take specimens from the wild.
Fortunately, these species are now on the prohibited list of the island’s Wildlife Protection Ordinance
(2013), so it is illegal to remove them from Ascension’s waters.
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The Offshore Marine Environment of Ascension Island, South Atlantic
Table 3. List of non-commercial fish species known to inhabit the offshore waters within the Ascension Island EEZ. Note that the Appendix to this report provides further
information on certain open water and deep water species (as indicated in column on the right).
Species
Common name
IUCN Red
List
Reference (listed by)
Notes
Featured
in
Appendix
Species likely to be found on the seabed, in deep water or associated with seamounts
Gymnothorax vicinus
Purplemouth moray
NE
Wirtz et al., 2014
To 145 m depth. A benthic and solitary species inhabiting rocky
shores and reefs where water is clear. Most active at night.
(Fishbase).
Trachinocephalus myops
Snakefish
NE
Wirtz et al., 2014
Burrows into sandy substrata, from 3–388 m. Listed by Fishbase as
Synodus myops.
Saurida brasiliensis
Brazilian lizardfish
NE
Wirtz et al., 2014
From 18–410 m depth, though usually from 50–198 m. Found close
to seabed. Found on the outer continental shelf. (Fishbase).
Diretmoides pauciradiatus
Longwing spinyfish
NE
Wirtz et al., 2014
From 0-600 m depth. Plankton eaters, with young near the surface
and older adults often descending to below 1,000 m depth.
Fistularia petimba
Red cornetfish
NE
Wirtz et al., 2014; Trunov, 2006
From 10-200 m. Doubtful record for Ascension (Wirtz et al., 2014) but
recorded from Grattan seamount (Trunov, 2006).
Pontinus nigropunctatus
St Helena deepwater
scorpionfish
LC
Wirtz et al., 2014; Trunov, 2006
From 146-183 m depth. Recorded from Grattan seamount (Trunov,
2006) and now from “close to Ascension” (Wirtz et al., 2014).
Scorpaena grattanica
Grattan scorpionfish
NE
Wirtz et al., 2014; Trunov, 2006
From 120-170 m depth. To date, this species is endemic to Grattan
seamount, and was first described by Trunov (2006). (See also Fig.
20).
Holanthias fronticinctus
St Helena seaperch
NE
Wirtz et al., 2014
Recorded from 120 m depth at Grattan seamount and also from
“close to Ascension” (Wirtz et al., 2014). Previously considered
endemic to St Helena and nearby Bonaparte seamount. However,
there is some disagreement as to this ID, as video footage of the fish
has it being identified as the Ascension swallowtail H. caudalis.
Serranus sanctaehelenae
St Helena comber
NE
Wirtz et al., 2014; Trunov, 2006
Recorded from both Ascension (Wirtz et al., 2014) and Grattan
seamount (Trunov, 2006). Endemic to St Helena, Ascension and
Grattan seamount.
Prognathodes dichrous
Bicolour or Hedgehog
butterflyfish
LC
Wirtz et al., 2014; Trunov, 2006
A reef-associated species, but included here as has been recorded
from Grattan seamount (Trunov, 2006). Endemic to St Helena,
Ascension and Grattan seamount.
Cookeolus japonicus
Longfinned bullseye
NE
Wirtz et al., 2014
From 40-400 m depth (usually, 165-200 m). Recent new record from
Ascension; also recorded from Grattan seamount (Wirtz et al., 2014).
Page 18 of 115

The Offshore Marine Environment of Ascension Island, South Atlantic
Species
Common name
IUCN Red
List
Reference (listed by)
Notes
Promethichthys
prometheus
Roudi escolar
NE
Wirtz et al., 2014
From 80-800 m depth (Usually 300-400 m). Found at continental
slopes, around oceanic islands and submarine rises. Migrate to
midwater at night. Feed on fish, cephalopods and crustaceans.
(Fishbase).
Ruvettus pretiosus
Oilfish
NE
Wirtz et al., 2014
From 100-800 m depth (usually 200-400 m). Usually over the
continental shelf, sometimes in oceanic waters down to 800 m.
Migrates far offshore. Pelagic. Feeds on fish, crustaceans and squid.
(Fishbase). New record for Ascension (Wirtz et al., 2014).
Featured
in
Appendix

Species likely to be found in mid-water
Coryphaena equiselis
Pompano dolphinfish
LC
Wirtz et al., 2014
From 0-400 m depth. Highly migratory species. Primarily an oceanic
species but may enter coastal waters. Usually forms schools. Follows
boats and may be found under floating objects. Feeds on small fishes
and squid. (Fishbase). Wirtz et al. (2014) qualify that this record
needs confirmation.
Coryphaena hippurus
Common dolphinfish
LC
Wirtz et al., 2014
Highly migratory species. Adults are found in open waters but also
near the coast. Form schools. Feed on almost all forms of fish and
zooplankton; also takes crustaceans and squid. (Fishbase).
Caranx bartholomaei
Yellow jack
NE
Wirtz et al., 2014
Adults prefer offshore reefs and open marine waters. Generally
solitary but sometimes seen in small groups. Feed on small fishes.
(Fishbase). A new record for Ascension (Wirtz et al., 2014).
Caranx crysos
Blue runner
LC
Wirtz et al., 2014
A schooling species, from 0–100 m depth. Of commercial interest
(particularly off the US eastern seaboard). Found both inshore and
offshore. Associated with Fish Aggregating Devices (FADs).
Caranx fischeri
Longfin crevalle jack
NE
Wirtz et al., 2014
Inhabits the subtropical waters of the east Atlantic Ocean. Mostly
found inshore, though appears to be able to travel long distances.
Only recently (2007) separated from C. hippos.
Caranx latus
Horse-eye jack
NE
Wirtz et al., 2014
From 0–140 m depth. A pelagic schooling species normally found
near offshore reefs. (Fishbase).

Caranx lugubris
Black jack
NE
Wirtz et al., 2014
Trunov, 2006.
From 12–354 m. restricted to clear oceanic waters. Not commonly
found in shallow banks. Sometimes seen near drop-off at outer edge
of reefs. (Fishbase). Also recorded from Grattan seamount (Trunov,
2006).

Decapterus macarellus
Mackerel scad
NE
Wirtz et al., 2014
From 40–400 m depth. Adults prefer clear oceanic waters, frequently
around islands. Feed mainly on zooplankton. (Fishbase).

Page 19 of 115

The Offshore Marine Environment of Ascension Island, South Atlantic
Species
Common name
IUCN Red
List
Reference (listed by)
Notes
Featured
in
Appendix
Decapterus punctatus
Round scad
NE
Wirtz et al., 2014
From 0–100 m depth. A shoaling species, generally near the bottom.
They feed on planktonic invertebrates, primarily copepods, but also
on gastropod larvae, ostracods and pteropods. Spawning occurs well
offshore year-round. Caught commercially and used for bait.
(Fishbase).
Elagatis bipinnulata
Rainbow runner
NE
Wirtz et al., 2014
From 0–150 m depth. Inhabits both coastal and offshore areas.
Attracted to FADs. Highly migratory (Fishbase). Known to venture
into inshore waters to feed on inshore species such as Melichthys
niger (AIG, 2014).
Pseudocaranx dentex
White trevally
NE
Wirtz et al., 2014
From 10–238 m depth (though usually 10-25 m). Adults form schools
at the surface, mid-water and close to the seabed. Associated with
reefs. (Fishbase).
Selar crumenophthalmus
Bigeye scad
NE
Wirtz et al., 2014
From 0–170 m (though usually 0–10 m). Adults prefer clear oceanic
waters around islands. Individuals travel in compact groups of
hundreds of thousands of fish. Mainly nocturnal in habit, they
disperse at night to feed on small shrimps, benthic invertebrates, and
forams when inshore, and zooplankton and fish larvae when offshore.
(Fishbase).
Seriola rivoliana
Longfin yellowtail
NE
Wirtz et al., 2014
From 5–245 m (though usually 30–35 m). Adults are benthopelagic in
outer reef slopes and offshore banks to 160 m or more. They form
small groups. Young often seen around floating objects. (Fishbase).
Seriola dumerili
Greater amberjack
NE
Wirtz et al., 2014
From 1-360 m (though usually 18-72 m). Adults found on deep
seaward reefs, feeding primarily on fishes such as the bigeye scad,
though also on invertebrates. Small juveniles associate with floating
plants or debris in oceanic and offshore waters. (Fishbase).
Trachinotus ovatus
Pompano
NE
Wirtz et al., 2014
From 50–200 m depth. Typically more of a reef species, often in
small shoals. (Fishbase).

Uraspis helvola
Whitetongue jack
NE
Wirtz et al., 2014
From 50-300 m. Adults benthopelagic in sandy bottoms at the foot of
the edge of outer reefs, either singly or in small shoals. (Fishbase).

Wirtz et al., 2014
Fishbase lists the Hound needlefish Tylosurus crocodilus crocodilus
(family Belonidae) as being present at Ascension. However, Wirtz et
al. (2014) list Tylosaurus sp., and state “it is currently unknown if the
western Atlantic T. acus (Lacepède, 1803) or the eastern Atlantic T.
rafale Collette & Parin, 1970 is present at Ascension”. Wirtz et al.


Species likely to be found close to the surface
Tylosurus sp.
Hound needlefish
Page 20 of 115
The Offshore Marine Environment of Ascension Island, South Atlantic
Species
Common name
IUCN Red
List
Reference (listed by)
Notes
(2014) point out that the species Tylosaurus imperialis (Rafinesque,
1810) was split into several subspecies, which have subsequently
been raised to species level. This needlefish is large, growing up to
1.5 m long.
Platybelone trachura
Ascension keeled
needlefish
NE
Wirtz et al., 2014
Endemic to Ascension and St Helena islands.
Cheilopogon
pinnatibarbatus
Bennett's flyingfish
LC
Wirtz et al., 2014
Found on both sides of the Atlantic, particularly around islands.
Feeds on zooplankton and small fishes.
Cheilopogon exsiliens
Bandwing flyingfish
NE
Wirtz et al., 2014
Cypselurus cyanopterus
Margined flyingfish
NE
Wirtz et al., 2014
Exocoetus volitans
Tropical two-winged
flyingfish
NE
Wirtz et al., 2014
Feed mostly on small crustaceans and other planktonic animals.
Preyed upon by swordfish, tunas and many other larger pelagic
fishes (Fishbase).
Hirundichthys rufipinnis
Redfin flyingfish
NE
Wirtz et al., 2014
From an original description by Kner & Steindacher (1867) of a fish
taken “from the south-west of Ascension”.
Scomberescox saurus
Atlantic saury
NE
Wirtz et al., 2014
From 0-30 m. Oceanic, schooling and gregarious. Feeds on
zooplankton and fish larvae. Preyed upon by fish, including tunas,
marlin bluefish and cod. (Fishbase). However, Wirtz et al. (2014)
states that the identification of this species requires verification, as
the recorded species for St Helena has now been changed to
Nanichthys simulans (Edwards & Glass, 1987).
Species ‘co-habiting’ with others
Echeneis naucrates
Live sharksucker
NE
Wirtz et al., 2014
Most abundant remora in warm waters. Coastal as well as oceanic.
Often found free-swimming in shallow inshore areas and around coral
reefs. Attaches temporarily to a variety of hosts including sharks,
rays, large bony fishes or sea turtles, whales and dolphins.
(Fishbase).
Remora albescens
White suckerfish
LC
Wirtz et al., 2014
Host specific on manta rays, but occasionally attaches to sharks
(including Whale sharks). Often occurs inside gill chamber and mouth
of host. Rarely free-swimming. (Fishbase).
Remora remora
Sharksucker
NE
Wirtz et al., 2014
Usually associated with sharks but also attaches itself to other large
fishes (including manta rays) and sea turtles. May be found in gill
chambers, fins and body surface. Sometimes free-swimming. Feeds
Page 21 of 115
Featured
in
Appendix
The Offshore Marine Environment of Ascension Island, South Atlantic
Species
Common name
IUCN Red
List
Reference (listed by)
Notes
on parasitic copepods. (Fishbase).
CR
Critically Endangered
EN
Endangered
NT
Near Threatened
VU
Vulnerable
LC
Least Concern
Page 22 of 115
DD
Data Deficient
NE
Not Evaluated
Featured
in
Appendix
The Offshore Marine Environment of Ascension Island, South Atlantic
2.4
Sharks and rays
Shark fisheries have rapidly expanded all over the world during the last three decades, so that today
several species are threatened. A number of local extinctions have already taken place, and a
considerable decrease in abundance has been observed for most species (Séret, 2005). The
continuing demand related to the production of medicinal products for the Asian market, as well as the
consumption of shark fin soup, together with the high prices of these products, are the main drivers of
this fishery. The function of sharks, as top predators at the end of the food chain, is however essential
to maintain the balances and the genetic quality of prey populations. The collapse of shark stocks,
beside the loss of biological diversity, represents a real threat to the sustainability of marine
ecosystems.
All species of sharks and rays which have been recorded from within the Ascension EEZ are listed in
Table 4. Those regarded as being Endangered or Near-threatened on the IUCN Red List of Threatened
Species are discussed in more detail below.
2.4.1
Endangered species
Just one species of shark considered to be Endangered has been reported from Ascension’s offshore
waters and that is the scalloped hammerhead Sphyrna lewini, though its presence has only recently
been recorded (Wirtz et al., 2014).
Scalloped hammerhead Sphyrna lewini
The scalloped hammerhead is a coastal pelagic species, found in warm temperate and tropical coastal
waters all around the globe between latitudes 46° N and 36° S. It has been recorded down to depths of
at least 275 m, though is most often found above 25 m. During the day, scalloped hammerheads tend
to be found closer to shore whilst at night they hunt further offshore. Adults occur alone, in pairs or in
small schools, while young sharks occur in larger schools. Adults spend most of the time offshore in
midwater, though females will migrate to the coastal areas to have their pups.
Research has shown that in parts of the Atlantic Ocean, scalloped hammerhead populations have
declined by over 95% in the past 30 years in several areas of its range, including South Africa, the
northwest and western central Atlantic and Brazil. This led in 2007 to the status of this shark species
being raised from Near Threatened to Endangered (Baum et al., 2007). Among the reasons for this
decline are over-fishing and the rise in demand for shark fins. This species' fins are highly valued
compared to other species (because of their high fin ray count) and they have been heavily targeted in
some areas (Baum et al., 2007).
All life-stages are vulnerable to capture as both target and bycatch in fisheries: large numbers of
juveniles are captured in a variety of fishing gears in nearshore coastal waters, and adults are taken in
gillnets and longlines along the coastal shelf and offshore in oceanic waters. It is reported that at
Ascension, groups of these sharks used to be seen at certain places close to the coast, though they are
rarely seen at these sites any longer.
The scalloped hammerhead is a member of the family Sphyrnidae, which is listed on Annex I, Highly
Migratory Species, of the UN Convention on the Law of the Sea.
Page 23 of 115
The Offshore Marine Environment of Ascension Island, South Atlantic
2.4.2
Near Threatened species
Four of Ascension’s shark species are considered to be Near Threatened according to the IUCN Red
List of Threatened Species.
Blue shark Prionace glauca
The Blue shark is an oceanic and epipelagic shark found worldwide in deep temperate and tropical
waters, from the surface to about 350 m depth. They feed on squid primarily but will also take pelagic
octopuses, a large number of bony fishes, small sharks and occasional sea birds. Whale and porpoise
blubber and meat have been retrieved from the stomachs of some captured specimens.
Blue Sharks are highly migratory with complex movement patterns. There tends to be a seasonal shift
in population abundance to higher latitudes associated with oceanic convergence or boundary zones as
these are areas of higher productivity. Tagging studies of blue sharks have demonstrated extensive
movements in the Atlantic with numerous trans-Atlantic migrations which are probably accomplished by
swimming slowly and utilising the major current systems (Stevens, 2009). Records from the Atlantic
show a regular clockwise migration within the prevailing currents (Compagno, 1984).
Although Blue shark appear abundant in areas where they are found, and they are fast-growing and
fecund (maturing in 4–6 years and producing average litters of 35 pups), there is concern over the
numbers which are being caught (an estimated 20 million individuals annually), mainly as bycatch. This
quantity is considered unsustainable (Stevens, 2009) and hence its Near-threatened status. (See also
section 3.1.1). However, this ‘near-threatened’ status is now being questioned: Reeves & Laptikhovsky
(2014), reviewing recent ICCAT assessments, state that “Atlantic Blue Shark are classified into
Northern and Southern stocks. In both cases, although the assessments are highly uncertain they
indicate that for both stocks the biomass is above that which would support MSY and that they are
currently harvested below the fishing mortality that would lead to MSY. This suggests that the current
level of exploitation is sustainable.”
Galapagos shark Carcharhinus galapagensis
The Galapagos shark has a widespread, but patchy distribution, occurring at many widely separated
island and some coastal sites in the Pacific, Atlantic and Indian Oceans (Bennett et al., 2003). They are
capable of crossing open oceans between islands and individuals have been reported at least 50 km
(31 miles) from land. The primary food of Galapagos sharks are benthic bony fishes (including eels, sea
bass, flatfish, flatheads, and triggerfish) and octopuses. They also occasionally take surface-dwelling
prey such as mackerel, flyingfish, and squid. As the sharks grow larger, they are reported to consume
increasing numbers of elasmobranchs (rays and smaller sharks, including of their own species) and
crustaceans. At Ascension, they are known to venture into inshore waters to feed on inshore fishes,
such as the plentiful blackfish Melichthys niger.
The Galapagos shark is classified globally on the IUCN Red Data List as Near Threatened, primarily
because populations at many sites may be subject to high levels of fishing pressure (e.g. tuna longline
fisheries, targeted drop-line fishing) and due to its slow reproductive rate (Bennett et al., 2003). The
population of Galapagos sharks at Ascension is also likely to be influenced by catches from nearshore
recreational/tourism-based angling.
In 1985, this was the most numerous shark species seen close to the island by divers, particularly off
the east side of the island around Boatswain Bird Island (R. Irving, pers. obs.). More recently, Tim
Hook, a knowlegeable Ascension angler (as reported by Wirtz et al., 2014), states that large groups of
dozens of differently sized individuals may be seen on occasion. The current sport-fishing world record
for this species (at 140 kg) is from Ascension Island (Wirtz et al., 2014).
Page 24 of 115
The Offshore Marine Environment of Ascension Island, South Atlantic
Tiger shark Galeocerdo cuvier
This large (>5.5 m long), omnivorous shark is common worldwide in tropical and warm-temperate
coastal waters. It is a relatively fast growing and fecund species. This species of shark is caught
regularly in target fisheries and as bycatch. The fins, skin and liver oil from Tiger Sharks are all
considered to be of high quality and can fetch good prices. Tiger sharks are taken as bycatch in a
variety of fisheries including tuna and swordfish longline fisheries, particularly those operating on, or
close to, the continental and insular shelves. There is evidence of declines for several populations
where they have been heavily fished, but in general they do not face a high risk of extinction. However,
continued demand, especially for fins, may result in further declines in the future (Simpfendorfer, 2009).
This species has probably the most diverse diet of any shark species. Prey includes numerous bony
fish, sharks, rays, turtles, sea birds, seals, dolphins, sea snakes, cephalopods, crabs, lobsters,
gastropods and jellyfish. They consume carrion and readily take baited hooks. Tiger sharks also have a
propensity to consume "garbage" of human origin, including plastics, metal, sacks, kitchen scraps and
almost any other item discarded in the sea (Randall, 1992).
In Georgetown, Ascension, there are photographs of large specimens (500+ kg) caught in the past on
display in the Saints Bar Club (Wirtz et al., 2014). Tim Hook states, “[Tiger sharks] are only around for 2
or 3 months (starting November/December). They arrive at the same time as the first Green turtles but
only stay for about half of the turtle season.” Tiger sharks have been seen cruising shallow beaches at
night, presumably searching for Green turtles (Wirtz et al., 2014).
Bluntnose sixgill shark Hexanchus griseus
The Bluntnose Sixgill Shark is wide ranging, although patchily distributed, in boreal, temperate and
tropical seas. It occurs from the surface to at least 2,000 m, on continental and insular shelves and
upper slopes (including seamounts). It feeds on a wide variety of animals including other sharks,
skates, rays, chimaeras, dolphinfish, small swordfish and marlins, herring, halibut, turbot, gurnards and
anglerfish, as well as many types of invertebrates including squid, crabs, sea cucumbers and shrimp
(Cook & Compagno, 2005). Adults tend to follow diurnal patterns of vertical distribution, sitting deep on
the bottom by day and coming toward or to the surface at night to feed.
Due to its broad depth range and relative sluggishness, this shark has often been captured incidentally
in fisheries for other species. It is taken by handline, longline, gillnet, traps, trammel net, and both
pelagic and bottom-trawls. It appears to be very vulnerable to overfishing, unable to sustain intensive,
targeted fisheries for long periods, and hence its Near threatened status (Cook & Compagno, 2005).
At Ascension, this species is only caught at night, frequently near the pipeline deepwater mooring off
Georgetown. The current sport-fishing world record for this species is from Ascension, at 589 kg (Wirtz
et al., 2014).
Whale shark Rhincodon typus
The whale shark is the world’s largest living fish, growing up to about 14 m long and weighing in the
region of 25 tonnes. It is also one of the most charismatic and unmistakable animals in the sea. This
enormous filter-feeding elasmobranch, with its unique checkerboard pattern of spots and stripes,
inhabits all tropical and warm temperate seas. They are known to migrate considerable distances, on
occasion to places where they can aggregate in large numbers. Ascension Island does not appear to
be such an aggregating location, with just lone individuals observed from time to time within the EEZ.
However, tracking studies have followed female whale sharks from the Caribbean region into the open
Atlantic and it has been suggested that these sharks may be seeking a suitable place in the tropical
mid-Atlantic to give birth (Heuter et al., 2013).
Page 25 of 115
The Offshore Marine Environment of Ascension Island, South Atlantic
Table 4. Species of sharks and rays (class Chondrichthyes) present within the Ascension Island EEZ.
Species
Common name
IUCN Red
List
Reference
Rhincodontidae
Rhincodon typus
whale shark
VU
Wirtz et al. 2014;
bigeye thresher shark
VU
Reeves & Laptikhovsky, 2014; Wirtz et al. 2014
shortfin mako shark
VU
Reeves & Laptikhovsky, 2014; Wirtz et al. 2014
Prionace glauca
blue shark
NT
Reeves & Laptikhovsky, 2014; Wirtz et al. 2014
Carcharhinus galapagensis
Galapagos shark
NT
Reeves & Laptikhovsky, 2014; Wirtz et al. 2014
Carcharhinus obscurus
dusky shark
VU
Reeves & Laptikhovsky, 2014; Wirtz et al. 2014
Galeocerdo cuvier
tiger shark
NT
Reeves & Laptikhovsky, 2014; Wirtz et al. 2014
scalloped hammerhead
EN
Reeves & Laptikhovsky, 2014; Wirtz et al. 2014
bluntnose sixgill shark
NT
Reeves & Laptikhovsky, 2014; Wirtz et al. 2014
Isistius brasiliensis
Cookie cutter shark
LC
Fishbase
Heteroscymnoides marleyi
Longnose pygmy shark
LC
Fishbase
pygmy shark
LC
Reeves & Laptikhovsky, 2014; Wirtz et al. 2014
Alopiidae
Alopias supercilliosus
Lamnidae
Isurus oxyrinchus
Carcharhinidae
Sphyrnidae
Sphyrna lewini
Hexanchidae
Hexanchus griseus
Dalatiidae
Squalidae
Euprotomicrus bispinatus
Page 26 of 115
Notes
The Offshore Marine Environment of Ascension Island, South Atlantic
Species
Common name
IUCN Red
List
Reference
Notes
Myliobatidae
Manta birostris
Giant manta
VU
Wirtz. et al., 2014
Manta sp. are listed as a protected species under AIG
Ordinance. In other parts of the world, manta rays are
frequently caught as bycatch by tuna fisheries. However,
they are not reported as a bycatch species within the
Ascension EEZ. Manta rays are known to be under threat
worldwide.
Mobula tarapacana*
Devil ray
DD
Wirtz. et al., 2014; J.Brown (pers. comm.)
Wirtz et al. (2014) list ‘Mobula sp.’ though J. Brown (the
island’s Fisheries Officer) has confirmed it as being M.
tarapacana.
CR
Critically Endangered
EN
Endangered
NT
Near Threatened
VU
Vulnerable
LC
Least Concern
Page 27 of 115
DD
Data Deficient
NE
Not Evaluated
The Offshore Marine Environment of Ascension Island, South Atlantic
Other shark species
A number of other shark species are known to occur within the ICCAT area, but whose presence has
still to be confirmed within Ascension EEZ waters. These are: Sandbar shark Carcharhinus plumbeus,
Longfin mako shark Isurus paucus, Night shark Carcharinus signatus, South Atlantic Silky shark
Carcharhinus falciformis, Porbeagle Lamna nasus, and Oceanic whitetip shark Carcharinus
longimanus.
The Oceanic whitetip shark is worthy of further mention. This species was once described as “nearly
ubiquitous in water deeper than 180 m and above 20°C” is now only occasionally recorded (Baum &
Myers, 2004), It was once the most common shark throughout the warm-temperate and tropical waters
of the Atlantic (Baum et al., 2006).
Page 28 of 115
The Offshore Marine Environment of Ascension Island, South Atlantic
2.5
Cetaceans
Our knowledge of cetacean species within Ascension’s offshore waters is patchy to say the least. Only
five (possibly six) species are known to occur, though the true number is likely to be more than this. By
means of comparison, within the eastern tropical Atlantic region, which extends from Mauritania south
to Angola, at least 34 cetacean species have been recorded (Weir & Pierce, 2013). Offshore records
within Ascension’s EEZ are likely to have come from ship-borne observers, with inshore records either
being taken from smaller craft or from the island’s cliffs. Occasionally, as has been the case with the
Gervais beaked whale specimens, individuals have been found washed up on the shore, either dead or
dying.
Ascension Island Conservation Department staff and volunteers have been monitoring whales and
dolphins in the waters around Ascension Island since 2001. Inshore sightings have been primarily of
bottlenose dolphins. This work is ongoing and the data collected are submitted into the Conservation
Department’s GIS system for future reference.
Table 5. Cetacean species recorded from within the Ascension Island EEZ.
Species
Common name
IUCN
Red List
Reference
Notes
LC
1
Listed under AIG Wildlife
Protection Ordinance, 2013
2
Uncertain as to whether S.
attenuata is present or not due
to possible confusion with S.
frontalis.
(see notes
below)
Delphinidae
Tursiops truncatus
Common bottlenose dolphin
[Stenella attenuata]
[Pan-tropical spotted dolphin]
Stenella frontalis
Atlantic spotted dolphin
DD
2
Humpback whale
LC
1
Sperm whale
VU
2
Gervais’ beaked whale
DD
1
Balaenopteridae
Megaptera novaeangliae
Physeteridae
Physeter macrocephalus
Ziphidae
Mesoplodon europaeus
CR
Critically Endangered
EN
Endangered
NT
Near Threatened
VU
Vulnerable
LC
Least Concern
DD
Data Deficient
1: Whales and Dolphins of Ascension Island. Leaflet & poster produced by the Ascension Island Government (no
publication date given). Available on-line at: http://www.ascension-island.gov.ac/wp-content/uploads/2013/01/
whales-and-dolphins-leaflet.pdf
2: Notes accompanying the Ascension Island stamp set Whales and Dolphins, issued 23 March 2009. Available
on-line at: http://www.the-islander.org.ac/artc_6352_ALL_2916_1.html.
Common bottlenose dolphin Tursiops truncatus
Common bottlenose dolphins are distributed worldwide throughout tropical and temperate inshore,
coastal, shelf, and oceanic waters. A recent minimum worldwide estimate of their abundance has been
given as 600,000 individuals (Hammond et al., 2012). Bottlenose dolphins consume a wide variety of
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The Offshore Marine Environment of Ascension Island, South Atlantic
prey species, mostly fish and squid though they may also eat shrimps and other crustaceans
(Hammond et al., 2012).
Within Ascension’s nearshore waters, bottlenose dolphins are considered ‘resident’ as they are present
throughout the year and may be seen all around the coastline, though particularly off the island’s east
coast. Recent studies have shown there to be two types of bottlenose dolphins worldwide, forming
distinct ‘inshore’ and ‘offshore’ groups. Those at Ascension are probably offshore dolphins, as these are
usually the ones that take up residency around offshore islands (Hammond et al., 2012). Offshore
individuals tend to be slightly larger, darker and have proportionally shorter fins and beaks than inshore
individuals.
Atlantic spotted dolphin Stenella frontalis
[Pantropical spotted dolphin Stenella attenuata]
Whilst the Pantropical spotted dolphin Stenella attenuata has been reported as being seen in
Ascension’s waters, there is some uncertainty as to whether or not this is a correct identification. The
Atlantic spotted dolphin Stenella frontalis appears very similar to the Pantropical spotted dolphin and
their shape is often described as an intermediate between a Bottlenose and a Pantropical spotted
dolphin (Hadoram & Jarrett, 2006). The colouration and patterns vary with age, lifestage and
geographic location, so it becomes very difficult to tell the two species apart. Atlantic spotted dolphins
are usually found in groups of fewer than 50 individuals, but have been occasionally seen in larger
groups of around 200 animals. The inshore/coastal pods usually consist of 5-15 animals. Atlantic
spotted dolphins are sometimes associated with other cetacean species such as bottlenose dolphins.
The smaller and less-spotted forms that inhabit more pelagic offshore waters and waters around
oceanic islands are less well known in their habitat requirements (Jefferson and Schiro 1997).
Pantropical spotted dolphins often occur in groups of several hundred to one thousand animals. They
are considered quite gregarious, often schooling with other dolphin species. Although specific migratory
patterns haven't been clearly described, they seem to move inshore in the autumn and winter months
and offshore in the spring. They feed primarily on mesopelagic cephalopods and fishes.
No information specific to spotted dolphins recorded within the Ascension EEZ has been discovered.
Humpback whale Megaptera novaeangliae
Seven major breeding stocks of Humpback whale are now recognized worldwide (Reilly et al., 2008).
Two of these occur in the Southern Atlantic: Stock A (Southwest Atlantic): coast of Brazil; and Stock B
(Southeast Atlantic): coast of West Africa from the Gulf of Guinea down to South Africa. It is uncertain
from which stock the small number of whales which regularly arrive at Ascension in September/October
are from. The Stock A population was reduced to a few hundred animals by the 1960s, being targeted
by Antarctic whaling operations centred on South Georgia, though it has now recovered to number over
6,500 (Reilly et al., 2008). The Stock B population was similarly depleted during the first half of the 20th
century by large catches in its wintering grounds off Gabon, Congo, Angola, Namibia and western
South Africa, though its numbers have also recovered (Reilly et al., 2008).
Humpback whales are known to undertake long migrations between breeding grounds in tropical
coastal waters in winter, to feeding grounds in middle and high latitudes. The Ascension humpbacks
may well have traveled from the Falkland Islands or even further south from the coastal waters of
Antarctica, a distance in the region of 7-8,000 km. Humpback whale calves have been seen at
Ascension too, but it is not known whether or not they have been born within Ascension’s waters.
Sperm whale Physeter macrocephalus
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The Offshore Marine Environment of Ascension Island, South Atlantic
It is not that surprising to find sperm whale as a cetacean species that has been recorded from within
Ascension’s EEZ. The habitat of the sperm whale is the open sea and they can be found in almost all
marine waters worldwide, deeper than 1,000 m, that are not covered by ice (Taylor et al., 2008a). Their
current Red List status is Vulnerable, owing to the fact that their population worldwide is proving very
slow to recover the losses inflicted from the days of commercial whaling. Within the Atlantic Ocean,
sperm whales tend to be sighted nearer to the continental margins of the ocean than close to the
centre. It would therefore be unusual for there to be many sightings of sperm whales around Ascension.
Gervais’ beaked whale Mesoplodon europaeus
At one time thought to be restricted to the North Atlantic, this species is probably continuously
distributed in deep waters across the tropical and temperate Atlantic Ocean, both north and south of the
Equator. It has been described as a ‘naturally rare’ species (Taylor et al., 2008b), and its Red List
status reflects this: Data Deficient. The species prefers deep waters based on the presence of prey
from such habitats in stomach contents and a lack of sightings near shore (Mead, 1989). Gervais’
beaked whales are known to feed primarily on squid, although some fish may be taken as well.
In 1980, three individual Gervais’ beaked whales stranded at Ascension in quick succession (AIG
cetacean leaflet). These were the first records of this species outside the North Atlantic (Mead, 1989). A
fourth animal stranded in March 2002. It is unclear why these strandings happened. Other strandings of
beaked whales elsewhere (including Gervais’ beaked whale) have been linked to disorientation thought
to have been caused by loud anthropogenic sounds, such as those generated by navy sonar and
seismic exploration (Taylor et al., 2008b). However, it is not known if this was the cause of these
strandings.
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The Offshore Marine Environment of Ascension Island, South Atlantic
2.6
Turtles
Turtles are a very ancient group of reptiles, whose collective ancestry can be traced back 100 million
years in the fossil record. There are seven species alive today. Marine turtles can be found in all
oceans of the world except for the polar regions. They are generally found in the waters over
continental shelves. After taking to the water for the first time, males will not return to shore again.
During the first three to five years of life, marine turtles spend most time in the pelagic zone, floating in
seaweed beds. Green sea turtles in particular are often found in Sargassum beds, a brown seaweed in
which they find shelter and food.
Two species of turtle frequent the nearshore waters around the island: the green turtle Chelonia mydas
and the hawksbill turtle Eretmochelys imbricata. Green turtles are far more numerous than hawksbills at
Ascension and use the island’s sandy beaches for egg-laying, particularly those on the west side of the
island. Whilst hawksbill turtles are regularly observed in the nearshore waters, they do not come ashore
to nest. The hawksbill turtles seen are probably sexually immature juveniles.
Table 6. Species of marine turtles recorded from within Ascension Island’s EEZ.
Species
Common name
IUCN Red List
Reference
Cheloniidae
Chelonia mydas
Green turtle
EN
Listed in Appendix I of CITES
Listed in Appendices I & II of CMS
Inter-American Convention for the Protection and
Conservation of Sea Turtles
AIG Wildlife Protection Ordinance, 2013
Green Turtle Species Action Plan (AIG, 2015a)
Eretmochelys imbricata
Hawksbill turtle
CR
Listed in Appendix I of CITES
Listed in Appendices I & II of CMS
Inter-American Convention for the Protection and
Conservation of Sea Turtles
AIG Wildlife Protection Ordinance, 2013
Leatherback turtle
VU
Listed in Appendix I of CITES
Listed in Appendices I & II of CMS
Inter-American Convention for the Protection and
Conservation of Sea Turtles
Memorandum of Understanding Concerning
Conservation Measures for Marine Turtles of the
Atlantic Coast of Africa
Dermochelyidae
Dermochelys coriacea
CR
Critically Endangered
EN
Endangered
NT
Near Threatened
VU
Vulnerable
LC
Least Concern
DD
Data Deficient
Green turtle Chelonia mydas
The green turtle grows up to 1.5 m in length and up to 300 kg in weight (AIG, 2015a). The natural
lifespan is thought to be about 80 years. It has a circumglobal distribution, occurring throughout tropical
and, to a lesser extent, subtropical waters. Whilst the population at Ascension appears to be doing very
well (a six-fold increase in the number of egg clutches deposited over 36 years, from approximately
3,700 to 23,700 clutches – Weber et al., 2014a), elsewhere the picture has not been so positive.
Extensive subpopulation declines have been reported in all major ocean basins over the last three
generations as a result of overexploitation of eggs and adult females at nesting beaches, juveniles and
adults in foraging areas, and, to a lesser extent, incidental mortality relating to marine fisheries and
degradation of marine and nesting habitats (Seminoff, 2004). Consequently, the IUCN Red List of
Threatened Species conservation status is set at Endangered.
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The Offshore Marine Environment of Ascension Island, South Atlantic
Since the discovery of the Ascension Island in the sixteenth century, the green turtle population has
been subjected to several centuries of exploitation for its meat. This intensified to a commercial scale
following permanent settlement of the island by the British in 1815, resulting in a severe depletion of the
population (Broderick et al. 2006). Harvesting had largely ceased by the 1930s when the operation
became uneconomical, and green turtles were legally protected in 1944 (Weber et al., 2014a).
The green turtle is a highly migratory species. For those returning to Ascension to nest and mate (both
females and males make the journey), they would have swum from coastal feeding areas off the coast
of Brazil, a distance of approximately 2,400 km, to reach the island (Mortimer & Portier, 1989). This is a
remarkable feat of navigation within the animal kingdom, with apparently very few clues to assist them
find their destination.
Foraging areas for adult green turtles from Ascension are off the Brazilian coast between Rio de
Janeiro and Forteleza. Juvenile green turtles originating from Ascension are even more widely
distributed, having been identified at foraging grounds along a 6000 km stretch of South American
coastline from northern Argentina to the Caribbean (Naro-Maciel et al., 2012). The adults are
predominantly herbivorous with a diet composed largely of seaweed and seagrass. During their journey
to Ascension, their nesting period and their return journey, they fast (or only eat very little). These
journeys are repeated every 3-4 years.
The green turtle nesting period on Ascension occurs between December and June. Hatchlings and
small juveniles are epipelagic omnivores and are thought to associate with floating vegetation and other
debris entrained in ocean currents (Witherington et al., 2012). The first five years of their lives are spent
in the open ocean and individuals are rarely seen. Indeed, what happens to individuals during these
‘lost years’ has long been a mystery for turtle biologists. One of their main predators during this time are
probably sharks – tiger sharks Galeocerdo cuvier are known to patrol Ascension’s shallow waters at
night during the nesting season (Wirtz et al., 2014). It has been estimated that, for the species as a
whole, as few as 1% of hatchlings are likely to reach sexual maturity (20+ years) (Hammerschlag et al.,
2015).
Recent work has investigated the ‘lost years’ conundrum of the green turtle using predictions of
transport within an Atlantic Ocean circulation model (Putman & Naro-Maciel, 2013). Utilising known
ocean current circulations, dispersal simulations were carried out using ‘virtual particles’, released at
both known nesting sites and foraging areas, which were then tracked.
Fig. 9. Predicted distribution of 13,500 particles tracked forwards in time from their release at
Ascension Island. (L) particle density counted daily; (R) mean age in years of particles. Taken from
Putnam & Naro-Maciel (2013).
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The Offshore Marine Environment of Ascension Island, South Atlantic
Fig. 9 shows the results of virtual particles being released from Ascension. It is clear to see that the
particles are taken in a westwards and south-westwards direction from the island towards the South
American coast, as one would expect. What is intriguing is to see that, by years 3-4, a considerable
density remains in the central Southern Atlantic, eventually traveling past the southern tip of Africa and
into the Indian Ocean. However, this model is predicting entirely passive drifting and takes no account
of a turtle’s ability to actively swim.
It is unclear how long hatchlings may spend in Ascension’s nearshore waters before embarking on their
journey westwards to the Brazilian coast. During their journey, they are likely to spend most of their time
close to the surface, to satisfy breathing requirements and also as it is likely to be the safest zone for
them to occupy. For post-nesting adults fitted with tracking devices, their journey back has been shown
to take a route that is almost due west from Ascension to the ‘bulge’ of the Brazilian coast, followed by
a period of extended coastal travel to their final destination (AIG, 2015a).
Hawksbill turtle Eretmochelys imbricata
Far less is known about the hawksbill turtles that visit Ascension than for green turtles. The hawksbill
turtle has a circumglobal distribution in tropical waters of the Atlantic, Indian and Pacific Oceans but has
undergone dramatic reductions in population size across its range due to overharvesting for meat,
shells and eggs (Mortimer & Donnelly, 2008).
It is only recently that any scientific studies have been undertaken on the population of hawksbill turtles
that occur around Ascension. Putman et al., (2014) conclude that 85% of hawksbills observed in
Ascension Island’s waters originate from nesting populations in north-eastern Brazil, with the remainder
linked to smaller rookeries in West Africa (e.g. São Tomé and Principe) and potentially even the Indian
Ocean. By tagging individual turtles over the past ten years (2003-2013), Weber et al. (2014b) found
that there was a mean minimum residence time of 4.2 years (range: 2.8–7.3 yr) and a mean growth rate
of 2.8 cm/yr. They concluded that Ascension serves as a mid-Atlantic developmental habitat for
benthic-feeding, juvenile hawksbill turtles on extended oceanic migrations before recruiting to their adult
foraging grounds, likely to be located in Brazil or tropical West Africa.
Leatherback turtle Dermochelys coriacea
Leatherback turtles are known to undertake long-distance, transoceanic migrations (Hays et al. 2004).
However, little was known of their migrations in the South Atlantic until 2006 when reports were
received of individuals which had been tagged in Gabon, West Africa stranding on the eastern shoreline
of South America. More recently, it has been shown that individuals travel in the opposite direction too
(Almeida et al., 2014): a tagged individual from a nesting beach in SE Brazil has turned up on a beach
in Namibia.
The presence of leatherback turtles within Ascension’s EEZ has only recently been confirmed. Fossette
et al. (2014) assessed known interactions of leatherback turtles with longline fishing vessels between
1995 and 2010 (see Fig. 10). The figure shows where high-fishing-pressure areas overlapped with
leatherback habitat use. It shows that within the Ascension EEZ there was both medium (high fishing
pressure/medium turtle use – shown in orange) and high (high fishing pressure/high turtle use – shown
in red) susceptibility of longline by-catch of leatherbacks.
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The Offshore Marine Environment of Ascension Island, South Atlantic
Fig. 10. Long-term susceptibility of leatherback turtle to bycatch in longline fisheries. This map
shows where high-fishing-pressure areas overlapped with leatherback habitat use, between
1995 and 2010, in the Atlantic Ocean. Three classes were defined: low (high fishing
pressure/low turtle use), medium (high fishing pressure/medium turtle use) and high
susceptibility (high fishing pressure/high turtle use). Nine main high-susceptibility areas were
identified (nos 1–9 on the map). These areas occurred both in international waters and in the
EEZs of 12 countries (in dark grey) fringing the Atlantic, including Ascension Island (United
Kingdom; ‘UK’, no. 7). Dashed grey lines represent the limits of national EEZs. Broken lines
represent latitudes 10° N and 10° S. Taken from Fossette et al., 2014.
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The Offshore Marine Environment of Ascension Island, South Atlantic
2.7
Seabirds
Ascension Island is the most important seabird
breeding site in the tropical Atlantic, supporting
approximately one million nesting seabirds of
11 different species (Table 7) (Oppel et al.
2015). Prior to 1815 (when the British
established a permanent garrison on the
island), the island was uninhabited and many
species bred all around the main island’s coast
and even on the low-lying plains. However,
both humans (in harvesting eggs) and feral
cats (taking chicks) have decimated numbers
Fig. 11. Masked booby on nest, Boatswainbird
of several species, and driven most to breed in
Island. Photo: R. Irving, 1985.
the relative safety of the offshore stack of
Boatswainbird Island. Feral cats were
successfully eradicated in 2006 (Ratcliffe et al., 2010) and since then a number of species have
successfully started to breed back on the mainland.
It has recently been shown by Croxall et al. (2012) that, worldwide, seabirds are more threatened than
other comparable groups of birds and that their status has deteriorated faster over recent decades. The
principal current threats at sea are posed by commercial fisheries (through competition and mortality on
fishing gear) and pollution, whereas on land, alien invasive predators, habitat degradation and human
disturbance are the main threats.
Table 7. Breeding seabirds on Ascension Island/Boatswainbird Island.
Species
Common name
IUCN
Red List
Population estimates (Oppel et al., 2015)
Fregata aquila
Ascension Island frigate bird
VU
Approx. 20,000 individuals (Ratcliffe et al.,
2008)
Sula dactylatra
Masked booby
LC
Approx. 4,600 individuals
Sula leucogaster
Brown booby
LC
Approx. 500 individuals
Sula sula
Red-footed booby
LC
Approx. 50 individuals
Onychoprion fuscatus
Sooty tern (aka Wideawake
tern)
LC
Approx. 350,000 individuals (Hughes et al.,
2012)
Gygis alba
Fairy tern (aka White tern)
LC
Anous minutus
Black noddy
LC
Anous stolidus
Brown noddy
LC
Phaethon aethereus
Red-billed tropic bird
LC
Phaethon lepturus
White-tailed tropic bird (aka
yellow-billed tropic bird)
LC
Oceanodroma spp.
Storm petrels
Oceanodroma castro
Madeiran storm petrel (aka
band-rumped storm petrel)
CE
EN
Critically Endangered
Endangered
Approx. 100 tropicbirds Phaethon spp. (both
Red-Billed and White-tailed)
_
NT
An IUCN Red List status is not possible when
no specific species is identified. See also
Table 9.
LC
Near Threatened
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VU
Vulnerable
LC
Least Concern
DD
Data Deficient
The Offshore Marine Environment of Ascension Island, South Atlantic
Ascension frigatebird Fregata aquila
The Ascension frigatebird is the island’s only endemic species of bird. It is classified by IUCN’s Red List
of Threatened Species as being Vulnerable (BirdLife International, 2012). Ascension frigatebirds have
been found to forage over a wide expanse of open ocean, incorporating much of the Territory’s 200 nm
EEZ and beyond into international waters (AIG, 2015b). The average foraging trip of a breeding adult
lasts 2-3 days and extends to a maximum distance of 200-300 km from the island. However,
displacements of over 1000 km have been recorded. Juveniles and non-breeding adults are even more
wide-ranging, occasionally appearing as vagrants along the coast of tropical West Africa (Ashmole et
al., 1994) and even as far north as Scotland (Wallbridge et al., 2003).
Ascension frigatebirds are pelagic surface-feeders and generally forage far from land over open ocean
(AIG, 2015b), probably in association with cetaceans and tuna schools that drive smaller prey species
within reach (Au & Pitman, 1988). Their diet appears to be more conservative than that of other
seabirds at Ascension Island, consisting almost entirely of flying fish of the genera Exocoetus,
Cypsilurus and Hirundichthyes (Stonehouse & Stonehouse, 1963). All prey is taken in flight as
frigatebirds cannot normally take off from the water. During certain seasons, small groups can also be
observed feeding on sea turtle hatchlings and sooty tern chicks over land. Kleptoparasitism of other
seabirds is known to occur but is not thought to form a significant part of the species’ diet (Ashmole et
al., 1994).
All of the other seabird species listed in Table 7 are known to forage in the waters of the EEZ.
Masked booby Sula dactylatra
Masked boobies nesting at Ascension Island forage over a wide expanse of open ocean, although
predominantly within the island’s 200 nm EEZ. On average, the foraging trips of breeding birds extend
to a maximum of 140 km from the Island, although occasional displacements of over 300 km have been
recorded (Oppel et al., 2015). Flying fish feature prominently in their diets, though at least 11 prey
species have been identified in regurgitates at Ascension Island, including large numbers of juvenile
redlip blennies Ophioblennius atlanticus (Dorward, 1962).
Masked boobies are amongst the most pelagic species of the Sulidae family, preferring to forage over
deep water (Schreiber & Clapp, 1987), often in association with subsurface predators such as dolphins
and yellowfin tuna Thunnus albacares (Au & Pitman, 1988). They obtain most of their prey by plunge
diving from a height of 10-30 m (AIG, 2015c), though they are only able to access prey within the top
two metres of the water column (Weimerskirch et al., 2009).
Sooty (Wideawake) tern Onychoprion fuscatus
Sooty terns are the most numerous seabird breeding on Ascension (AIG, 2015d), with as many as
350,000 birds (175,000 nests) breeding each season (Hughes et al., 2012). However, historically,
Hughes (2014) estimates that the breeding population numbered approximately 2.8 - 3 million birds
between 1877 and 1958, prior to a decrease in prey availability linked to the rapid expansion in
commercial long-lining for tuna in the tropical Atlantic Ocean.
The foraging distribution of sooty terns during the breeding season is not known (AIG, 2015d). Between
breeding seasons sooty terns are pelagic and highly migratory, seldom approaching land. Tracking
studies suggest that Ascension birds predominantly forage far to the north of the Island during the nonbreeding phase, exploiting the productive waters of the equatorial central Atlantic.
Sooty terns are highly pelagic and are generally only found close to land around breeding periods. Their
diet consists mainly of small pelagic fish and squid caught at or near the surface of the ocean
(Ashmole, 1963). Sooty terns rely heavily upon prey driven within reach by small, surface-schooling
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The Offshore Marine Environment of Ascension Island, South Atlantic
tuna such as skipjack Katsuwonus pelamis and yellowfin Thunnus albacares and are seldom seen
feeding independently of them in oceanic waters (Au & Pitman, 1988).
Table 8 lists migrant (non-breeding) seabird species which have been recorded within 200 nm of
Ascension (Bourne & Simmons, 1998).
Table 8.
Migrant (non-breeding) seabird species recorded within 200 nm of Ascension.
Unconfirmed/dubious sightings have been left out. After Bourne & Simmons (1998).
Common name
Trinidade petrel
Scientific name
Position seen / Notes
Pterodroma arminjoniana
10.5°S 16.1°W (180 nm SSW Ascension)
Originally called a Herald petrel subspecies, but now split into
3 separate species (Brooke, 2004). Only breeds on Trindade
and Martin Vaz Islands off the coast of Espírito Santo, Brazil.
One on board HMY Britannia at 12.5°S 09.4°W (24Jan1957);
Bulwer’s petrel
Large skua
Bulweria bulwerii
Catharacta sp.
05.6°S 15.0°W, 200 nm north (01Feb1985); 70 nm north
(16Apr1986); 10.0°S 10.0°W, 150 nm SE (17Nov1988); from
North Point (17Nov1988); and (31Oct1997)
Seen twice at sea, 1957-59; and offshore (Apr1977); two
(18Feb1987); 3 miles off Geordetown (18Sep1993);
06Nov1996; and going south (10Oct1997).
One at 04.5°S 15.5°W (16Feb1983); 05°11′S 14°52′W
Pomarine skua
Stercorarius pomarinus
(29Nov1983); 05.6°S 15.0°W (10Feb1985) – all about 200
nm north of Ascension. One harrying black noddies offshore
(Dec1993).
Two at 10.5°S 16.1°W, 180 nm SSW (02Oct 1982); three 70
Arctic skua
Stercorarius parasiticus
Long-tailed skua
Stercorarius longicaudus
Arctic tern
Sterna paradisaea
nm to north (08May1984); three at 05.2°S 14.9°W, 200 nm to
north (29Nov1983); at least four 200 nm to north
(23Nov1988); mup to 37 daily offshore (20-24Nov1988); one
chasing noddies off North Point (11Mar1990).
11 at 10.5°S 16.1°W, 180 nm SSW (02Nov1982); four 02.8°S
17.9°W (23Nov1988); pale immature heading south
(16Oct1989)
19 at 10.5°S 16.1°W, 180 nm SSW (02Noc1982); one at 08.4
°S 13.1°W offshore (19Nov1988).
Hughes et al. (2014) have recently analyzed a series of seabird sightings data (of both resident and
migratory birds) from 1957 to 2011 and have concluded that there appears to be an area to the northwest of Ascension which is favoured by various species which they have called an ‘assembly site’ (Fig.
12). The two main findings of their study are that (1) waters to the north-west of Ascension Island are
more highly used by pelagic seabirds than those to the south or the east of the island; and (2) the
assembly site that they have identified for seabirds is partly within the EEZ of Ascension Island. They
also state that “Seabird assembly sites can be explained by food availability and we predict that the
waters in local areas along the South Equatorial Current in the NW segment may be more productive
for seabirds that forage at higher trophic levels than the waters elsewhere in the tropical Atlantic
Ocean”.
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The Offshore Marine Environment of Ascension Island, South Atlantic
Fig. 12. At-sea sightings of one or more seabirds of the same species in the middle of
the tropical Atlantic Ocean between 1957 and 2011 (inclusive). The four sighting classes
were defined as ‘low’ (0-4 sightings), ‘medium’ (5-9 sightings), ‘high’ (>90th percentile)
and ‘potential assembly sites’ (highest number of sightings). Taken from Hughes et al.,
2014. [Note that the grey circle denotes the limit of the study area in question, which was considerably larger
than the 200 nm EEZ limit around Ascension].
Hughes et al. (2015) also list the species of seabirds which had been recorded on two or more
occasions in the vicinity of the ‘assembly site’ to the N-NW of the island, together with their general
breeding locations (Table 9).
Table 9. Pelagic seabird species recorded on two or more occasions in the assembly site at 14–16°W
and 4–6°S N–NW of Ascension Island, South Atlantic, together with their breeding locations. After
Hughes et al., 2015.
Arctic
Antarctic
Mid-latitude
Tropical Islands
Long-tailed Jaeger
Stercorarius longicaudus
Great Shearwater
Puffinus gravis
Cory’s Shearwater
Calonectris diomedea
Red-footed bobby
Sula sula
Parasitic Jaeger
Stercorarius parasiticus
Sooty Shearwater
Puffinus griseus
Leach’s Storm Petrel
Oceanadroma leucorhoa
Masked Booby
Sula dactrylatra
Pomarine Skua
Stercorarius pomarinus
White-bellied Strom Petrel
Fregetta grallaria
Ascension Frigatebird
Fregata aquila
Arctic Tern
Sterna paradisaea
Wilson’s Storm Petrel
Oceanites oceanicus
Bulwer’s Petrel
Bulweria bulwerii
Common Tern
Sterna hirundo
Red-Billed Tropicbird
Phaethon aethereus
Sooty Tern
Onychoprion fuscatus
Black Noddy
Anous minutus
Brown Noddy
Anous stolidus
Band-rumped Storm Petrel
Oceanodroma castro
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The Offshore Marine Environment of Ascension Island, South Atlantic
2.8
2.8.1
Marine molluscs and other invertebrates
Marine molluscs
The phylum Mollusca has both terrestrial and marine representatives and includes slugs and snails
(which together make up about 80% of all known mollusc species), bivalves and cephalopods, the last
group including octopuses, squids and cuttlefishes. Cephalopods, particularly the squids, form an
important part of the diet of several seabird species.
Very little is known of the molluscan fauna in the waters surrounding Ascension; considerably more is
known of the nearshore molluscan fauna (for instance: Rosewater, 1975). The accepted way of
obtaining mollusc specimens on the sea bed for identification purposes has been by using a deep sea
dredge. The author has only come across one expedition which used such a dredge off Ascension –
the Challenger Expedition of 1872-1876. The ship HMS Challenger called by at Ascension towards the
end of her epic 4½ year scientific cruise around the world in March 1876. The dredge samples obtained
(as included in a subsequent paper by Edgar Smith in 1890 entitled On the marine mollusca of
Ascension Island) came from “420 fathoms [768 m] off the west side of Ascension Island”, though the
exact latitude and longitude is not recorded. Nine species of mollusca were recorded by Smith (1890)
from the dredge sample, out of a total of 42 species recorded “from Ascension” (Table 10).
Table 10. List of mollusca which have been recorded from Ascension Island’s ‘offshore’ zone (i.e. not
from shallow, nearshore waters, typically less than 50 m depth).
Species
(as originally recorded)
Notes
Species
(as recognized currently)
Gasteropoda (sic)
Eulima chyta Watson, 1883
Eulima chyta Watson, 1883
Rissoa (Setia) tenuisculpta
Watson
Name changed to Cingula tenuisculpta (in
Rosewater, 1975) and now to Talassia
tenuisculpta (Watson, 1873)
Talassia tenuisculpta
(Watson, 1873)
Rissoa (Setia) triangularis R.
Boog Watson, 1886
Name now changed to Setia triangularis
(Watson, 1886)
Setia triangularis (Watson,
1886)
Basilissa oxytropis Watson, 1879
This is no longer a recognised species. The
‘closest’ species name is Basilissa alta var.
oxytoma Watson, 1879, which is now renamed
as Hadroconus altus (Watson, 1879)
?
Utriculus oryctus Watson
This is no longer a valid genus, and the species
is not recognised at all. Rosewater (1975) lists
this species as Retusa orycta (R. Boog Watson,
1883), but this species too is no longer
recognised.
?
Cylichna cylindracea (Pennant,
1777)
Cylichna cylindracea
(Pennant, 1777)
Scaphopoda
Dentalium entalis var. agile
Dentalium entalis is listed as a species in its own
right and as having three variants. Var. agile is
not one of these variants. Dentalium entalis has
now been renamed as Antalis entalis (Linnaeus,
1758). Listed by Rosewater (1975) as Dentalium
(Antalis) agile M. Sars, 1872
Pelecypoda [Bivalvia]
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Antalis entalis (Linnaeus,
1758).
The Offshore Marine Environment of Ascension Island, South Atlantic
Species
(as originally recorded)
Notes
Species
(as recognized currently)
Cryptodon sp.
There were 38 species belonging to the genus
Cryptodon in 1890. The genus no longer exists,
with all species being allocated to various other
genera.
?
Nuculana jeffreysi (Hidalgo,
1877)
The genus Nuculana still exists (originally
encompassing over 200 species and subspecies!) though there is no record of jeffreysi as
being one of its species.
?
The nearshore molluscan fauna is listed by Rosewater (1975), and features 89 species. Amongst these
are a number of pelagic species which would certainly be found offshore as well as closer to the shore.
The violet sea snail Janthina janthina (Linnaeus, 1758) is one such, first being collected from the nests
of sooty terns. It is concluded that these birds are likely to have picked up the snails far out to sea and
carried them to shore as food. Janthina janthina is found worldwide in the warm waters of tropical and
temperate seas, floating at the surface by means of a special ‘raft’ they create out of air bubbles. These
snails are therefore part of the pleuston, organisms living on or at the very surface of the water. They
are pelagic, drifting on the surface of the ocean, where they feed upon pelagic hydrozoans, especially
the by-the-wind sailor Velella velella and the Portuguese man o' war Physalia physalis.
The common octopus Octopus vulgaris (Fig. 13) has been recorded from Ascension in nearshore
waters (Rosewater, 1975). “Dredged in 20-30 fathoms [36-54 m]”. This particular specimen was taken
on the Challenger expedition at the same time as the dredged material, though all cephalopod
specimens for the entire voyage of HMS Challenger were described by Hoyle (1886) rather than by
Smith (1890).
Fig. 13. Common octopus Octopus vulgaris, photographed at Ascension by John Taylor
in 1985 as part of ‘Operation Origin’, a diving expedition to catalogue the island’s
nearshore habitats and species.
Other cephalopod species (particularly squid) are also likely to feature within the offshore waters of the
EEZ, particularly deep water pelagic (i.e. mostly meso-pelagic) species. Many of these species reside
in the depths during daylight hours but will migrate to the surface during darkness to feed on planktonic
organisms near the surface. Several seabird species present on Ascension include these deep-water
cephalopods in their diet, and it should be possible to identify the partially digested remains of the
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The Offshore Marine Environment of Ascension Island, South Atlantic
cephalopods from the stomach contents of these birds. The beaks of the cephalopods take a long time
to digest and it is possible to identify a cephalopod species from just its beak.
2.8.2
Other marine invertebrates
The biota of the deep seafloor features many other invertebrate species, but as far as the author has
been able to ascertain, no published reports have been produced on any such studies. However,
besides molluscs, it is likely that sessile organisms would include various sponges, anemones, corals,
sea fans and sea whips, bryozoans and sea squirts. Mobile species would probably feature various
worms, crustacea, sea cucumbers, brittlestars and starfish. See also section 2.10.1.
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The Offshore Marine Environment of Ascension Island, South Atlantic
2.9
Seamounts
It is thought there may be as many as 100,000 seamounts (which rise at least 1,000 m) scattered
throughout the world’s oceans, but only 0.4% (~400) of these have actually been explored and of these,
only 100 have been sampled in any detail. Deep-sea scientists have recently catalogued over 30,000
seamounts for the internationally collaborative CenSeam project (Census of Seamounts) which began
in 2005 as part of the larger Census of Marine Life project.
Seamounts are considered to be important for several reasons:

They provide excellent case studies for the understanding of marine biodiversity patterns.
Seamounts vary greatly in their biodiversity; they may have a high degree of endemism; they may
act as centres of speciation; and they may provide a role as "stepping stones" for the dispersal of
coastal species.

They are areas of high production that support commercially important fisheries and, particularly in
the Pacific Ocean, coral mining.

They are fragile ecosystems that must be managed carefully and with good scientific information in
order to prevent habitat damage.
At least five distinct seamounts have been identified within the Ascension EEZ. The small amount of
research that has been carried out on investigating them has tended to concentrate on their topography
and not so much on their ecology. Consequently, the generalized description of seamounts given here
is not specific to the Ascension EEZ seamounts, although much of it will be relevant.
As a result of their very nature in forming very large, prominent structures on the sea floor, seamounts
can have a considerable influence on the oceanic conditions found in their vicinity. They can affect
oceanic currents resulting, amongst other things, in local concentrations of plankton which in turn attract
species that graze on it. They have been shown to act as highly effective natural aggregating devices
for tuna and other migratory species, primarily for feeding but also possibly for breeding too. They also
may serve as way stations in the migration of whales and other pelagic species. Each may host
elevated concentrations of biological diversity (compared with the surrounding sea floor) and each is
likely to have its own unique ecosystem.
No two seamounts are the same: each will have its own set of physical features and conditions, which
in turn affect the marine life associated with it. Differences in seabed morphology will influence
hydrodynamic flow patterns and therefore the deposition of sediment and organic matter (Clark et al.,
2010). Complex current patterns can also influence sea life above them. Strong localized currents and
upwellings can lead to increased concentrations of plankton over seamounts and this, combined with
the constant influx of prey organisms, means that they can attract large numbers of fish. Thus, the
physical presence of seamounts has been shown to support relatively large planktonic and higher
consumer biomass when compared to surrounding ocean waters, particularly in oligotrophic oceans (as
is the case within the Ascension EEZ).
Some seamounts have been shown to support high levels of biodiversity and unique biological
communities. In some instances high levels of endemic species (only found at that locality) have been
found. Seamounts may act as regional centers of speciation, stepping stones for dispersal across the
oceans and refugia for species with a shrinking range. Cetaceans, sharks, tuna, and cephalopods all
congregate over seamounts to feed, and some seabirds have been shown to be more abundant in the
vicinity of shallow seamounts.
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The Offshore Marine Environment of Ascension Island, South Atlantic
Fig. 14. Bathymetric profile across the central Atlantic Ocean, showing the location of Ascension
Island in relation to the ocean basin margins and the Mid-Atlantic Ridge. Vertical exaggeration
1:150. Adapted from the Submission made by the United Kingdom of Great Britain and Northern Ireland to
the Commission on the Limits of the Continental Shelf in regard to Ascension Island on 9 May 2008.
2.9.1
Physical descriptions of seamounts within the Ascension EEZ
Of the five distinctive seamounts present within the Ascension EEZ, three have their summits less than
320 m from the sea surface (Fig. 15 and Table 11). Two of these have been named (Gratton and Harris
Stewart), while the third still awaits to have a name recognised by the Undersea Feature Names
Gazetteer (http://www.ngdc.noaa.gov/gazetteer/) of the General Bathymetric Chart of the Oceans. The
summits of the other seamounts remain in deep water (i.e. greater than 800 m from the surface).
Fig. 15. The location of three of the main seamounts within the Ascension Island EEZ. Note that
Ascension itself is in the exact centre of the EEZ circle. (Courtesy of Ascension Island Government
Conservation Department).
The local bathymetry for Grattan Seamount is shown in Fig. 16, and that for the Harris Stewart
Seamount in Fig. 17 below. Grattan Seamount is also referred to in the literature as the Grattan Bank,
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The Offshore Marine Environment of Ascension Island, South Atlantic
as it can be seen there is another smaller seamount lying close to the west of the main one, with a
distinct ‘valley’ between them.
Table 11. Distinctive seamounts within the Ascension Island EEZ.
Name of seamount
Grattan
Harris Stewart
Location
Shallowest point / ref.
9° 44′ S 12° 49′ W
72 m below surface (Edwards, 1993); 70 m (Hect &
(260 km SE of Ascension Is.)
Malan, 2007)
8° 28′ S 16° 58′ W
(305 km WSW of Ascension Is.)
Unnamed*
90 km E of Grattan Seamount
Unnamed
7° 50’ S 14° 35’ W
(“Northern”)
(20 km NW of Ascension)
Unnamed
8° 57’ S 14° 38’ W
(“Southern”)
(116 km SW of Ascension)
265 m below surface (Hect & Malan, 2007)
316 m below surface (Reeves & Laptikhovsky, 2014)
800 m below surface (Faneros & Arnold, 2003)
1500 m below surface (Faneros & Arnold, 2003)
* It is possible that this seamount is the one known elsewhere as ‘Circe’.
Fig. 16. Seabed beathymetry in the vicinity of Grattan seamount.
Image taken from internet site: http://earthref.org/cgibin/sc.cgi?id=SMNT-097S-0128W
One of the Ascension angling boats (Shy III) travelled to the Grattan Bank in March 2006 and reported
their catch by means of an on-line blog (http://www.marlinnut.com/forums/t4903/). Captain Ian Carter
reported “small yellowfin tuna, small billfish, small wahoo and a large blue marlin; and at deeper depths
caught grouper, bullseye, oilfish, black jacks and small sharks.” He supposed that “…this was the first
time a sport boat had ever been there.”
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The Offshore Marine Environment of Ascension Island, South Atlantic
Fig. 17. Seabed beathymetry in the vicinity of Harris Stewart
seamount. Image taken from internet site: http://earthref.org/cgibin/sc.cgi?id=SMNT-085S-0170W
Fig. 18. Sun-illuminated (i.e. viewed from
directly overhead) bathymetry for an
unnamed seamount (“Northern”), lying just to
the north-west of Ascension). The shallowest
part of the seamount is approximately 800 m
below the surface, the deepest part being at
about 3,600 m depth and with a basal
diameter of 16 km. [Image taken from
Faneros & Arnold, 2003].
Fig. 19. Sun-illuminated bathymetry for an
unnamed seamount (“Southern”), lying
approximately
116 km
south-west
of
Ascension. It is approximately 19 km long by
9 km wide. The base is in a water depth of
3,200 m and the summit at 1,500 m. [Image
taken from Faneros & Arnold, 2003].
Faneros & Arnold (2003) named the two seamounts they investigated (Figs. 18 & 19) “Northern” and
“Southern” for simplicity’s sake. They concluded that the Northern Seamount’s close proximity to the
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The Offshore Marine Environment of Ascension Island, South Atlantic
Ascension volcano, the correlation of the seamount’s summit with the northwest trending ridge of
Ascension, and the overlapping relationships deposits with the basal portion of the Ascension volcano
suggests that the seamount originated as Ascension flank eruptions. With regard to the Southern
Seamount, the orientations of it to the ridge and graben structures that so closely parallel the MidAtlantic Ridge, indicates that the Southern Seamount probably originated from Mid-Atlantic Ridge
volcanic processes, as apposed to hot-spot related processes suggested for Ascension Island (Faneros
& Arnold, 2003).
A further, named seamount (Stvor Guyot) is present between the Ascension Fracture Zone and the
Bode Verde Fracture Zone to the south, approximately 930 km ESE of Ascension (and thus outside the
EEZ).
2.9.2
Ecological description of seamounts within the Ascension EEZ
During the course of his research for this review, the author has only come across one paper written on
a biological subject matter for any of the seamounts within the Ascension EEZ, and that has been on
the fish fauna of the Grattan Bank (Trunov, 2006). Trunov (2006) describes fish samples that were
taken during Russian research cruises from 1973-1975 which visited a number of seamounts in the
mid-Atlantic, collected by seine nets of pelagic and bottom trawls. He provides no description of the
other marine life encountered nor of any of the habitats. He describes one species new to science and
named Scorpaena grattanica, a species
of scorpionfish (Fig. 20).
The international Census of Seamounts
project has led to many new discoveries
in the deep oceans from all parts of the
globe, but particularly in the Pacific
Ocean. Even before the project, any
ecological investigation of a seamount
was likely to come up with numerous
species new to science. De Forges et al.
Fig. 20. Scorpaena grattanica, a new species of
(2000) reported on the discovery of more
scorpionfish (Family Scorpaenidae) from Grattan
than 850 macro- and megafaunal species
Seamount, described and illustrated by I.A. Trunov
from seamounts in the Tasman Sea and
(2006).
southeast Coral Sea, of which 29–34%
were new to science and potential seamount endemics. They proposed that the low species overlap
between seamounts in different parts of the region indicated that the seamounts in clusters or along
ridge systems function as ‘island groups’ or ‘chains,’ leading to highly localized species distributions
and apparent speciation between groups or ridge systems that is exceptional for the deep sea. Their
results have substantial implications for the conservation of this fauna, which is threatened by fishing
activity.
With regard to seamounts present in the mid-Atlantic, Edwards (1993) points out that a number of the
seamounts in the region are likely to act as stepping stones in the distribution of their fish faunas (Fig.
21). Several species originally thought to be endemic to a restricted location or locations have now
been found to have wider ranges, although these are still restricted to their own isolated seamounts or
island fringes. Wilson & Kaufmann (1987) estimated the endemism of fishes and invertebrates on
seamounts as 12% and 15% respectively, though De Forge et al. (2000) reported their investigations of
SW Pacific seamounts to indicate endemism levels as high as 22-36%. Clearly, it is highly likely that
these levels of endemism will fall as more studies are undertaken on seamount ecology, or at least the
range over which their endemicity extends will increase.
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The Offshore Marine Environment of Ascension Island, South Atlantic
Fig. 21. Map of central South Atlantic area between the islands of Ascension
and St Helena to show locations of shallow (< 200m deep) seamounts.
(Based on British Admiralty Chart 4007.) (After Edwards, 1993).
More recently, in 2011, a National Geographic expedition obtained ROV video footage of the marine life
associated with the plateau of the Grattan Seamount. This was the first time video had been obtained
from the site (http://www.expeditions.com/blog/2011/11/21/first-look-at-a-tropical-seamount-2/). The
plateau appeared covered with various species of coral, anemones and numerous fishes. Of the fishes,
two species proved to be of particular interest: the Bicolour butterflyfish Prognathodes dichrous (only
previously recorded from, and thus an endemic of, St Helena and Ascension); and a small anthias, the
Ascension swallowtail Holanthias caudalis (known only from Ascension) though misidentified initially as
the very similar St Helena basslet H. fronticinctus. So these findings fit in with the ‘stepping stone’
hypothesis, extending the known range of both of these endemic species.
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The Offshore Marine Environment of Ascension Island, South Atlantic
2.10
Deep-sea and pelagic biodiversity
2.10.1 Benthic communities of the deep sea
For animals of the deep-sea floor, geographical patterns in the distribution of species (or higher taxa)
and the causes of those patterns are not well known. This situation arises, in part, because of the great
mismatch between the vastness of the habitat and the small amount of sampling that has been done. In
addition, large numbers of species are present in the deep sea, most of which are undescribed. Further,
the number of specialists who can provide identifications or taxonomic descriptions is small and is
decreasing (Thistle, 2003).
Compared with the North Atlantic, the deep-sea benthos of the Equatorial Atlantic, and that of the South
Atlantic, is poorly known. Most studies have concerned the abundance, diversity and distribution of
particular groups, such as ascidians (Monniot, 1979), protobranch bivalves (Allen & Sanders, 1996) and
echinoderms (Sibuet, 1979).
The organisms which constitute the benthic communities can be separated by their chosen method of
feeding. Deposit feeders (such as various worm-like animals including polychaetes, oligochaetes,
nemerteans, echiurians and sipunculids) ingest sediment. Suspension feeders feed on material they
collect from the water column, intercepting epibenthic plankton, particles raining from above, and
particles that have been resuspended from the seabed. These can be divided into active suspension
feeders (e.g. barnacles and sponges); and passive suspension feeders (e.g. crinoids, some holthurians,
some ascidians). Carnivores/predators (which will include many of the demersal fishes) select and
consume living prey. In the food-poor deep sea prey are rare, so the time between encounters with prey
will be long compared to that needed to subdue and ingest a prey item once encountered. That leaves
detritivores and the specialised carcass feeders: at peak abundance around a fish carcass, tens of
fishes, hundreds of amphipods, and hundreds of brittlestars may be present (although these peaks are
not simultaneous). These abundances are many times greater than abundances in the background
community, so carcasses will cause local concentrations of individuals (Thistle, 2003).
Rocky outcrops that rise above the sediment ooze, or offer sheer or overhanging faces which avoid
having particulate matter accreting on them, provide a firm foothold for the attachment of sessile
organisms. These will include deep sea corals, such as gorgonian branching corals and sea whips,
erect and branching sponges, sea anemones and erect bryozoans. Associated mobile benthic
megafaunal organisms will include various starfish and brittlestars, holothurians, crabs and shrimps,
and gastropod molluscs; macrofaunal organisms consist primarily of polychaetes, bivalve molluscs, and
isopod, amphipod, and tanaid crustaceans; and finally the meiofauna consists of primarily of
foraminifers, nematodes, and harpacticoid copepods.
2.10.2 Demersal communities
Very little information is known about the communities inhabiting the demersal zone close to the ocean
floor within the EEZ. They are likely to feature deep-sea demersal fishes, certain species of shark,
cephalopods and, from time to time, transitory visitations by sperm whale.
Those fishes which have been recorded, or are expected to be recorded, within this zone are presented
in Table 12, with further information summarised in the Appendix. A query of the FishBase on-line
database (using the search terms ‘Ascension Island’ and ‘deep water’) revealed 26 species likely to
inhabit this zone within the EEZ.
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The Offshore Marine Environment of Ascension Island, South Atlantic
2.10.3 Mid-water pelagic communities
Pelagic communities that inhabit the water column itself range in size from the great whales to minute
copepod crustaceans. They include nektonic organisms (i.e. those that can swim against currents if
need be) such as cephalopods (octopus and squid) and mesopelagic fishes; and planktonic organisms
(i.e. those whose movements are heavily influenced by currents) such as medusa, ctenophores,
doliolids and siphonophores. Many of these species will undertake vertical migrations through the water
column, a pattern often dictated by movements of zooplankton. However, the diversity, abundance and
distribution of pelagic organisms inhabiting this zone is very poorly known, despite this ecosystem being
by far the largest on Earth!
The decomposition of organic matter, together with animal respiration, reduces the oxygen
concentration in the water column, producing an oxygen-minimum layer in mid-water, usually between
300m and 1000m depth. Recent research into this Oxygen Minimum Zone (OMZ), which in the eastern
tropical Atlantic is at around 400 m depth, has found that this zone has been expanding at a rate
greater than that seen elsewhere, leading to a habitat reduction for large, active predatory fish such as
marlin (http://www.mbari.org/expeditions/GOC15/Leg2/ February25.html).
2.10.4 Near-surface communities
Little information is available on near-surface oceanic communities. The Ascension region appears to
be sandwiched between two areas of primary production: the Eastern Tropical Atlantic (to the east and
north) and the South Atlantic Tropical Gyre (to the south and west). Some areas correspond, in broad
terms, to areas where the food supply to the benthos is seasonally pulsed, others to areas where the
benthic food supply is more continuous.
Recent work by Hughes et al. (2014) indicates an area to the north-west of Ascension which they have
termed an ‘assembly site’ and which appears to be favoured by foraging seabirds. It is possible this
could indicate a particularly productive area of sea, fed by upwelling currents and generating denser
quantities of primary producers (i.e. phytoplankton) than surrounding areas. However, this suggestion
remains speculative until further research work can be undertaken.
The upper layers of the ocean support the whole range of ecological producers and consumers, ranging
from phytoplankton and zooplankton, through various swimming invertebrates and open ocean fishes,
to predatory sharks and cetaceans. Table 3 (section 2.2) lists various open water fishes present within
the Ascension EEZ; Table 4 (section 2.3) lists those sharks and rays which may be encountered; and
Table 5 (section 2.4) lists the cetaceans. The three species of turtle (Green, Hawksbill and
Leatherback) which are on migration routes when passing through the offshore area of the EEZ, should
also not be forgotten.
2.10.5 Non-biological deep sea resources
Whilst the Pacific Ocean tends to be better known for its manganese nodules than the Atlantic, such
nodules do exist on the seafloor of the Atlantic though in discrete regions. Manganese nodules are
composed of a mixture of iron and manganese oxides and were first recovered from the Atlantic near
the Canary Islands during the Challenger Expedition (1872-1876). They are most extensively
developed in the Argentine, Brazil and Cape Basins in the South Atlantic and in the Sargasso Sea in
the North Atlantic. These Atlantic nodules have a somewhat lower manganese content (16%) and
higher iron content (21%) than those in the Pacific and Indian Oceans (Brown et al., 1989). Despite
their presence in the Atlantic, and even their association with seamounts, it is thought unlikely that they
would be present within the Ascension EEZ and highly unlikely, if present, to be there in commercially
viable quantities. For many years the technology was not available to extract manganese nodules in
commercially viable quanitites, but the hardware and techniques are now being developed for
experimental extraction projects to begin.
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The Offshore Marine Environment of Ascension Island, South Atlantic
Table 12. Fish species thought to inhabit ‘deep waters’ within the Ascension Island EEZ.
Species
Dalatiidae
Euprotomicrus bispinatus
Isistius brasiliensis
Ophichthidae
Herpetoichthys regius
Common name
IUCN
Reference
Red List
Notes
Appendix


Pygmy shark
Cookie-cutter shark
LC
LC
Wirtz et al., 2014
Fishbase (DW)
Ornate snake eel
NE
Wirtz et al., 2014
NE
Fishbase (DW)


Also recorded by Trunov (2006) as Ophichthus regius from Grattan
seamount.
Cetomimidae
Ditropichthys storeri
Derichthyidae
Derichthys serpentinus
Narrownecked oceanic eel
NE
Wirtz et al., 2014
Nemichthyidae
Nemichthys scolopaceus
Slender snipe eel
NE
Wirtz et al., 2014
NE
Wirtz et al., 2014

Fishbase (DW)
Fishbase (DW)
Fishbase (DW)
Fishbase (DW)
Fishbase (DW)
Wirtz et al., 2014
Fishbase (DW)





Günther’s boafish
NE
NE
NE
NE
NE
NE
NE
Gigantura
Telescopefish
NE
NE
Wirtz et al., 2014
Wirtz et al., 2014


Opah
NE
Wirtz et al., 2014

Topside lampfish
NE
Fishbase (DW)

Platytroctidae
Barbantus elongatus
Stomiidae
Astronesthes caulophorus
Astronesthes micropogon
Astronesthes niger
Chaudiolus minimus
Echiostoma barbatum
Eustomias intermedius
Stomias affinis
Giganturidae
Gigantura chuni
Gigantura indica
Lampridae
Lampris guttatus
Myctophidae
Notolychnus valdiviae
Diretmidae
Threadfin dragonfish
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
The Offshore Marine Environment of Ascension Island, South Atlantic
Diretmoides pauciradiatus
Diretmus argenteus
Zenionidae
Zenion longipinnis
Gempylidae
Diplospinus multistriatus
Gempylus serpens
Lepidocybium flavobrunneum
Nealotus tripes
Promethichthys prometheus
Symphysanodontidae
Symphysanodon berryi
Trichyuridae
Aphanopus intermedius
CE
Critically Endangered
EN
Longwing spinyfin
Silver spinyfin
NE
Fishbase (DW)
Fishbase (DW)

NE
Wirtz et al., 2014

Striped escolar
Snake mackerel
Escolar
Black snake mackerel
Roundi escolar
NE
NE
NE
NE
NE
Fishbase (DW)
Fishbase (DW)
Fishbase (DW)
Fishbase (DW)
Wirtz et al., 2014




Slope bass
NE
Fishbase (DW)

Intermediate scabbardfish
NE
Wirtz et al., 2014

Endangered
NT
Near Threatened
VU
Vulnerable
LC
Least Concern
Page 52 of 115
DD
Data Deficient
NE
Not Evaluated
The Offshore Marine Environment of Ascension Island, South Atlantic
2.11
Oceanic microflora / microfauna
The tropical ocean region is made up of oligotrophic waters characterized by low primary productivity
and consequently a low secondary productivity (Melo et al., 2014). Despite low densities, tropical
zooplanktonic communities have as their primary characteristic a high species richness, which in turn
results in a large network of trophic interactions in which this community participates (Piontkovski &
Landry, 2003). Within this complex network of interactions, copepods play a significant role in the
transfer of energy and organic material from primary producers to the higher trophic levels in pelagic
ecosystems, accounting for as much as 80% of the biomass of planktonic metazoans in the marine
environment. Copepods are considered the most abundant and diverse components of
mesozooplankton in marine environments and the most important secondary producers in marine food
webs. Variations in the abundance, distribution and interactions within the community of planktonic
copepods are strongly related to the hydrographic characteristics of the marine environment.
The presence of islands and seamounts is responsible for variations in the hydrodynamics of the
environments where these features occur, generating a diversity of physical and ecological processes
which in turn influence the structure of several local communities (Genin 2004) and promote the
creation of unique habitats for many species.
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The Offshore Marine Environment of Ascension Island, South Atlantic
3.
Conservation needs and threat assessment
3.1
The sustainability of high seas fisheries
The main target species of the longline fishery, whose distribution encompasses part of the Ascension
Island EEZ, is bigeye tuna Thunnus obesus. This longline fishery operates over a wide area of the
tropical Atlantic (Reeves & Laptikhovsky, 2014). Other species have also been targeted, most notably
swordfish Xiphias gladius, yellowfin tuna Thunnus albacares, blue marlin Makaira nigricans and sailfish
Istiophorus albicans (platypterus). Reeves & Laptikhovsky (2014), in their review of fisheries
management for Ascension Island waters, concluded that the relevant stocks for bigeye tuna and for
swordfish were currently being fished sustainably. The stock assessment for yellowfin tuna was more
uncertain but they concluded that it was probably being fished sustainably. However, there were
indications that the stocks for both blue marlin and sailfish were currently being overfished (Table 13).
The longline method of fishing that is used by vessels operating in the tropical mid-Atlantic (undertaken
mostly by vessels from Taiwan and Japan) involves the use of longlines. The longline consists of a
main line to which baited hooks are attached at intervals by means of secondary branch lines
(sometimes called snoods). These are short lengths of line, attached to the main line using a clip or
swivel, with a single hook at the other end. Longlines are classified mainly by where they are placed in
the water column. Those used in the vicinity of Ascension tend to be set at depths greater than 100 m
(J. Brown, pers. comm.).
Huang (2013) describes the fishing gear used on the Taiwanese vessels as follows: “The bigeye tuna
vessels deploy 3,000 hooks per set. The main line (monofilament nylon) is 90 to 150 km long.
Secondary branch lines are about 40-50 m in length and have light sticks connected to the 4.2-inch J
hooks. Squid, mackerel and milkfish are used as bait. The vessels spend 6-9 hours setting lines and
approximately 12-19 hours hauling.”
Table 13. Reported total catches by species and entry year for licensed vessels fishing in the
Ascension EEZ, 2011 to 2013 (from Reeves & Laptikhovsky, 2014).
Year:
No. of trips:
Tuna
Billfish
3.1.1
Total
2011
176
2,972.3
144.9
67.6
199.4
30.3
11.6
100.5
0.0
224.5
3,751.1
2012
99
1,543.3
64.6
29.6
116.2
12.0
0.4
11.3
5.7
120.9
1,904.0
2013
91
1,503.5
75.6
37.8
218.2
5.9
2.1
22.6
35.1
121.2
2,022.1
Estimated value (£1,000)
14,245.4
7,265.6
7,616.0
Bigeye
Yellowfin
Albacore
Swordfish
Black Marlin
Striped Marlin
Blue Marlin
Sailfish
Other
The ‘problem’ of bycatch
The term ‘bycatch’ can be broadly defined as “the incidental capture of non-target species”. Bycatch
may be discarded (i.e. thrown back into the sea either alive or dead) or it may be retained on board the
vessel if it has value and if it is allowed to be landed back at port (i.e. within a size limit or a quota
allowance).
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Longline fishing results in significant bycatch. In order to assess this problem, Taiwan was required to
initiate an observer programme in 1999 (Huang, 2011). Not all of the Taiwanese vessels have
observers on board however – details of the coverage are given by Huang (2011). Typically, about 5%
of vessels will have observers on board4, which means that 95% will not and their catch data will simply
be written down into logbooks. Logbook information has been recognised as notoriously unreliable,
usually involving significant under-reporting and incorrect species identification, meaning that accurate
estimates can only be achieved through programmes that use well-trained observers (Paleczny et al.,
2015; Baum et al., 2003).
Another problem with the catch data that are recorded for these longline vessels has been that it is not
always noted whether or not the vessel has been fishing within the Ascension EEZ.
Huang et al. (2009) include information on bycatch species for the period 2002-2006. In terms of the
proportion of the total catch that could be assigned as bycatch, their ‘other’ category (i.e. noncommercial fish species) amounted to 35.1% of the observed catch. Of this ‘other’ category, 51.6% was
Blue shark, 10.8% was other sharks, and the remaining 37.6% was other fish species. The ‘other’
category figure of 35.1% for the period 2002-2006 had apparently fallen to between 6.0% and 6.3% for
the period 2011 to 2013, as reported by vessels in the Ascension EEZ (Reeves & Laptikhovsky, 2014).
Reeves & Laptikhovsky (2014) point out that this suggests sharks, and particularly Blue sharks, are
likely to be a major component of the ‘other’ catch category within the Ascension EEZ (Table 14). As
shark-finning is illegal in Taiwan (Reeves & Laptikhovsky, 2014), the presumption is that catches of
sharks are taken for human consumption or possibly as trade in other countries. Other shark species of
particular concern that are caught by commercial longlining vessels as bycatch in Ascension include
Galapagos sharks, bigeye thresher sharks and oceanic whitetip sharks.
Table 14. Estimated species composition of sharks and other fish in catches by vessels licensed to fish
within the Ascension EEZ, 2011 to 2013 (from Reeves & Laptikhovsky, 2014). [Note that these figures
do not relate to actual catches within the EEZ].
Catches reported in the ‘other’ category are first “raised” to account for presumed discarding using the
specified raising factors, then the species compostion of the raised estimates is obtained using the bycatch
rates given in Huang et al. (2009).
Year:
Catch of ‘other’ fish as reported
2011
224.5 t
2012
120.9 t
5.53
2013
121.2 t
Raising factor
5.86
Raised estimate of ‘other’ fish caught
1,316.6 t
668.3 t
5.85
709.7 t
Estimated catch of Blue Shark
678.9 t
344.6 t
366.0 t
Estimated catch of other sharks
142.5 t
72.4 t
76.8 t
Estimated catch of other fish species
495.1 t
251.3 t
266.9 t
The extraction of sharks by longlining has been identified as being a significant factor in the changes
which have befallen the pelagic fish community in the Pacific since the 1950s, when industrial fishing
commenced (Ward & Myers, 2005). It was found that, since the start of fishing, a major shift in size
composition, species abundance and community biomass took place. The largest and most abundant
predators, such as sharks and large tunas, suffered the greatest declines in abundance (21% on
4
Taiwan initiated their fisheries observer programme in 1999 (Huang, 2011). The average coverage achieved over
2002 to 2006 was 5.3% of trips in all Atlantic tuna longline fisheries. The number of vessels participating in these
fisheries varies from year to year. In 2006, there were 15 vessels fishing for Bigeye tuna; in 2007, this increased to
60 vessels; and in 2012, 75 Taiwanese vessels were authorised to fish for Bigeye tuna and 59 for Albacore
(ICCAT, 2014).
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The Offshore Marine Environment of Ascension Island, South Atlantic
average). Ward and Myers (2005) also found striking reductions in mean body mass. For example, the
mean mass of blue shark Prionace glauca was 52 kg in the 1950s compared to 22 kg in the 1990s. The
estimated abundance of this species was 13% of that in the 1950s. Overall, the biomass of large
predators fell by a factor of 10 between the periods. Of the three possible explanations put forward to
explain these data (fishing, environmental variation, and sampling bias), available evidence indiated
fishing to be the most likely cause for the observed patterns.
Of course, the Pacific is not the Atlantic, and there will be differences in fleet sizes and catch effort, but
there are some lessons which should be taken into consideration when appraising longlining in the
Atlantic. There are two main factors which make assessing the impact of commercial fisheries on the
pelagic communities of the Ascension EEZ so difficult. Firstly, there is no observer category for fishing
which takes place solely within the EEZ; and secondly, both target species (i.e. tunas, swordfish, blue
marlin, sailfish etc,) and bycatch species (sharks, other non-commercial fish species, turtles etc.) are
mobile and may swim freely in or out of the EEZ on routes which may vary from year to year depending
on environmental conditions.
In order to try to minimize the quantity of bycatch that is caught, a number of adaptations have been
shown to have succeeded in some longline fisheries. Such mitigation techniques include the use of
weights to ensure the lines sink quickly; the deployment of streamer lines around the vessel when
deploying baited longlines to scare away birds; setting lines only at night in low light (to avoid attracting
birds); limiting fishing seasons to the southern winter (when most seabirds are not feeding young); and
not discharging offal while setting lines.
For the Taiwanese longline fishing fleet, Huang (2011) provides information on the mitigation measures
that have been introduced to address bycatch issues. These include measures to promote the live
release of sharks, seabirds and turtles; the prohibition of shark finning; and the prohibition of retaining
on board oceanic whitetip, hammerhead or bigeye thresher sharks. Huang (2011) also notes that the
Taiwanese have also conducted research on such measures as using circle hooks as a means of
reducing bycatch of species such as turtles, though it was concluded that no significant difference was
seen between the use of J-hooks and circle hooks for sea turtle bycatch.
Apart from certain shark species (blue shark, Galapagos shark, bigeye thresher shark and oceanic
whitetip shark) and certain other fishes, the impact of bycatch on turtles, seabirds and cetaceans
appears to be ‘very low’, according to Reeves & Laptikhovsky (2014). For instance, from data published
by Huang et al. (2009) and interpreted by Reeves & Laptikhovsky (2014), the annual catch of seabirds
across the whole Taiwanese fleet in the tropical tuna industry was estimated at 20 birds per year for the
period 2002 to 2006. Similarly for turtle bycatch during the same period (2002-2006), between latitudes
0 ° and 10 ° S and by interpreting data from Huang et al. (2009) and Huang (2013), Reeves &
Laptikhovsky (2014) estimate the annual catch of turtles within this latitude range as being 100 per
year. Of these, they state, 60 would be Leatherbacks and one a Green turtle. Around 40% would be
released alive. For cetacean bycatch, Huang et al. (2009) noted that, for the period 2002 to 2006 for the
Taiwanese fleet fishing in the Atlantic with observers on board, a total of 27 individual cetaceans were
captured, and that most captures were made in the tropical zone. No further information is given on
these individuals.
3.1.2
The attraction of seamounts to high seas fisheries
Seamounts seem to favour aggregations of marine predators (tunas, dolphins, seabirds) in their vicinity
(Morato et al. 2008; Pitcher et al. 2007). They have been identified as hotspots of pelagic biodiversity in
the open ocean (Samadi et al., 2006), though the evidence for this is not as clear as first seemed (Clark
et al., 2010).
Biological communities on seamounts face a number of threats from human activities. The most widely
known of these is fishing, especially trawling, although in recent years the potential has increased for
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The Offshore Marine Environment of Ascension Island, South Atlantic
exploitation of mineral resources too (more so in the Pacific however, than in the Atlantic). Seamount
communities are extremely vulnerable to the impacts of fishing: their limited fixed habitat, the extreme
longevity of many species (of the order of 100 years and more – see Table 15 below), and the
apparently limited recruitment between seamounts, all compound the uncertainty of recovery from
trawling, which sweeps away the benthic epifaunal community as a bycatch (De Forges et al., 2000).
In the 1970s, extensive trawling began on seamounts as fleets discovered large aggregations
associated with them (Clark et al. 2007). Orange roughy Hoplostethus atlanticus have been targeted on
seamounts worldwide, with roundnose grenadier Coryphaenoides rupestris being a major seamount
fishery in the North Atlantic. Smaller fisheries for alfonsino Beryx splendens, mackerel, and black
cardinalfish Epigonus telescopus have occurred in the mid-Atlantic and elsewhere. Few of these largescale seamount trawl fisheries have proved sustainable, with many showing a boom-and-bust pattern
(Vinnichenko, 2002).
Many deep-sea commercial species have characteristics that generally make them more vulnerable to
fishing pressure than shallower shelf species (Clark et al., 2010). They can form large and stable
aggregations over seamounts for spawning or feeding, which enables very large catches and rapid
depletion of stock size. Biological factors such as longevity, low fecundity, and slow growth rates make
recovery from fishing impacts slow. Seamount fisheries have typically proven difficult to research and
manage sustainably. Once overexploited, it is uncertain if deep-sea fisheries on seamounts can
recover, and irregular recruitment levels may be a key factor (Clark, 2001).
Many seamount taxa are extremely long-lived and grow very slowly, especially those forming biogenic
habitats (some scleractinian corals) and those adding structural complexity (e.g., large erect
anthipatharian and gorgonian corals, sponges, and crinoids) (Table 15). Some of these low-productivity
components of benthic ecosystems on seamounts can therefore be expected to have less capacity to
absorb human disturbance and take much longer to recover than their shallower, more productive
counterparts (Clark et al., 2010).
Table 15. Examples of age estimates of seamount invertebrate megabenthos (from Clark et al., 2010).
Faunal group
Glass sponge
Stalked crinoid
Zoanthid (Gerardia spp.)
Age (years)
440
340
Method
Ring count
14C dating
14C dating
Reference
Samadi et al. 2007
Samadi et al. 2007
Roark et al. 2006
Zoanthid (Gerardia spp.)
Gorgonian coral
1800
67–2377
14C dating and ring count
14C dating
Rogers et al. 2007
Roark et al. 2006
Bamboo coral
35–197
14C and 120Pb dating
Rogers et al. 2007
Biogenic habitat (accumulated)
1000–50,000
U/Th dating
Rogers et al. 2007
3.2
3.2.1
400–900
Offshore impacts on species also found inshore
Foraging seabirds
The number of seabirds caught by incidental capture in pelagic longlines is thought to be very low (Yeh
et al., 2013), probably because of the preference for active prey with the consequence that they do not
generally pursue fishing vessels in search of discards (Huang, 2011).
Several of Ascension’s seabird species however rely, indirectly, on the presence and behaviour of tuna
(and other large fish species) in order to catch their prey (Au & Pitman, 1988). Tuna species,
particularly yellowfin Thunnus albacares, in pursuance of their own prey, tend to drive smaller pelagic
fish to the surface. In the case of flyingfish, they are likely to glide above the surface of the sea during
these chases in order to escape being caught by the tuna. Flyingfish, particularly of the genus
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The Offshore Marine Environment of Ascension Island, South Atlantic
Exocoetus, form the principal diet of both boobies and frigatebirds, which they obtain near or above the
sea surface (Oppel et al., 2015). Sooty terns are also reliant upon large schools of surface-swimming
tuna to drive their prey within reach (Au & Pitman, 1988). Consequently, there is heavy reliance on the
presence of tuna schools within the foraging ranges of these seabirds.
Atlantic stocks of large tuna species have declined by an estimated 50–80% over the past 50 years and
there is some evidence of impacts on Ascension’s seabirds (Hughes, 2014). It would appear that
fisheries for the Atlantic yellowfin and bigeye tuna are currently regarded as sustainable by the regional
regulator (ICCAT, 2014), though it is known that there has been a long term decline in their populations
since the 1960s (Cullis-Suzuki & Pauly, 2010). Indeed, this period of decline corresponds to an
apparent collapse in the size of the Ascension Island sooty tern population by almost 90% (Hughes,
2014). A dietary shift in chick provisioning also appears to have occurred during this period, with a
significant decline in the proportion of fish and a corresponding increase in the proportion of squid,
which has a lower nutritional value (Hughes, 2014). Again, overfishing has been implicated in this shift,
with a decline in the availability of small fish driven to the surface by schooling tuna during the day
forcing terns to switch to alternative food items, such as squid that tend to be active on the surface at
night (Hughes, 2014). If tuna stocks continue to be overfished, impacts on the remaining sooty tern
population are likely to be significant (AIG, 2015d). As pointed out in the Species Action Plans for the
Ascension frigatebird, the masked booby and the sooty tern, any further depletion of tuna stocks as a
result of overfishing would therefore be expected to have severe consequences in terms of reduced
food availability and diminished breeding success (AIG, 2015b).
It has been proposed that the importance of Ascension as a seabird breeding station relates to its
position within a zone of elevated productivity driven by the westward flowing South Equatorial Current
(Scullion, 1990). Any changes in current strength and position as a result of climate change could
therefore have significant impacts on the productivity of the marine ecosystem and food availability for
seabirds at Ascension Island. Indeed, mass seabird breeding failures periodically occur at Ascension
Island and there is circumstantial evidence to suggest that these are related to climate anomalies such
as the El Niño Southern Oscillation (AIG, 2015b).
3.2.2
Sharks
Following the advent of tagging studies, many shark species have been found to be highly migratory,
traveling long distances during their lifetimes. These include tiger shark (max. recorded distance
between tagging and recovery of tag of 3,430 km), bigeye thresher shark (2,767 km), shortfin mako
(3,433 km), dusky shark (3,800 km). Galapagos sharks are also known to be capable of crossing open
oceans between islands, with individuals being reported at least 50 km from land.
No definitive population assessments of shark species known to occur within the Ascension EEZ have
been undertaken. However, it is apparent that large numbers of sharks are taken as bycatch during
longlining operations. Blue shark, shortfin mako, and bigeye thresher shark are all classed as being
‘most vulnerable stocks’ within the ICCAT area (Reeves & Laptikhovsky, 2014). Bigeye thresher sharks
are also known to be significant to Taiwanese fisheries, which land about 220 metric tons annually.
(Joung et al. 2005).
The Galapagos shark is the most common shark species seen in the nearshore waters around
Ascension. Anecdotal evidence suggests their numbers are thought to be increasing again, having
been depleted for a number of years. The shark has a widespread but patchy worldwide distribution,
occurring at widely separated islands and some coastal sites in the Pacific, Atlantic and Indian Oceans
(Bennett et al., 2003). In 1982, it was reported as being a “very common species” at St Paul’s Rocks, a
small archipelago of barren islets on the Mid-Atlantic Ridge to the north-west of Ascension at 00°55′N;
29°21′W (Edwards & Lubbock, 1982). Indeed, the shark population was described as being “one of the
densest shark populations of the Atlantic Ocean”, consisting largely of Galapagos Carcharhinus
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The Offshore Marine Environment of Ascension Island, South Atlantic
galapagensis and silky Carcharhinus falciformis sharks (Edwards & Lubbock, 1982). However, for the
past decade, no sharks have been observed around the islets despite the occurrence of several diving
expeditions, and the population of Galapagos sharks there is now recognised as being extinct (Luiz &
Edwards, 2011). The sharks’ demise is the result of intense fishing pressure by commercial fishing
vessels operating around the islets throughout the year. The persistence of occasional individuals of the
once locally common silky shark in the vicinity of the archipelago, as a result of constant immigration of
this oceanic species from outside the area, suggest that the population might recover if the present
fishing pressure was removed (Luiz & Edwards, 2011). This episode should be borne in mind when
considering not only Ascensions’ shark populations but also those of neighbouring seamounts.
3.2.3
Turtles
Incidental capture in fisheries constitutes a major source of mortality for marine turtles worldwide and
may affect green turtles, both in their coastal foraging habitats and during oceanic migrations. The
migration route between Brazil and Ascension Island traverses an area of intensive pelagic longlining
for tuna and billfish (AIG, 2015a). Although thousands of marine turtles die as a result of long-lining
activities worldwide, green turtles account for a relatively small proportion of this total (Angel et al.,
2014), with most studies in the southern and central Atlantic reporting a by-catch rate of 0-13
individuals per million hooks (Sales et al., 2008; Coelho et al., 2013). The herbivorous diet and
predominantly coastal distribution of adult green turtles probably explain this reduced susceptibility,
although specific data from along oceanic migration routes where risks may be elevated is lacking. In
contrast, by-catch rates of green turtles in coastal trawl and net fisheries in the south-west Atlantic are
substantial (Wallace et al., 2013; Gallo et al., 2006) and may impact both adults and juvenile stages
originating from Ascension Island.
3.3
Conservation needs of the wider pelagic environment of the tropical
Atlantic
From studies that have been undertaken on Ascension’s nearshore marine wildlife, it is apparent that
their origins derive from both sides of the Atlantic. This is likely to be the case with a number of deep
sea species too. The predominant current affecting the island flows from east to west, leading to the
expectation that there should be more species whose geographical spread extends further to the east
than to the west. However, this is not necessarily the case. The growing use of mitochondrial DNA as a
research tool investigating speciation may well determine many new species or species groups, as well
as extending the known ranges of other species (e.g. Muss et al., 2001). Ascension’s marine wildlife
represents a unique mix of eastern and western Atlantic biodiversity.
3.3.1
The need for a Reference Area within the tropical Atlantic system
As far as the author is aware, there are no large-scale benthic or pelagic ‘reference areas’ within the
tropical Atlantic. Reference areas provide extensive areas of ocean that are free from commercial
fishing operations, and thus provide an opportunity for comparing fished and non-fished ecosystems.
Without such areas for comparative purposes, it is not possible to assess properly the impact which
extractive fishing activities might be having on individual species or certain habitats. Reference areas
also provide scientists with an opportunity to undertake monitoring of natural variability and long-term
change within ecosystems in areas free of the disturbances caused by human activities.
The UK has led the way in promoting the establishment of such scientific reference areas. Indeed,
having a reference area was one of the main justifications behind the UK’s successful Commission for
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The Offshore Marine Environment of Ascension Island, South Atlantic
the Conservation of Antarctic Marine Living Resources (CCAMLR) proposal to create the South Orkney
MPA in 2009 (http://archive.ccamlr.org/pu/E/e_pubs/cm/11-12/91-03.pdf). The area in question, the
South Orkney Islands southern shelf, was acknowledged “as being of high conservation importance,
and representative of key environmental and ecosystem characteristics in the region”.
Other reference areas have also been proposed around the Antarctic landmass. In 2012, the UK
proposed the establishment of a network of scientific reference areas along the length of the Antarctic
peninsula in areas where ice sheets collapse. Other reference areas were also being proposed at the
time by Australia, New Zealand and the United States for areas of the Antarctic coastal shelf over which
they had jurisdiction.
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4.
Conclusions
4.1
Sources, quality and extent of information

This Review provides a comprehensive assessment of what is known about the offshore
marine environment surrounding Ascension Island in the South Atlantic. Sources have included
peer-reviewed literature and grey literature, expert opinion and personal experience.

Where known, species inventories have been presented, with notes on their conservation
status, worldwide distributions and local importance.

Most information is known about the island’s resident seabird populations and the annual visits
of nesting green turtles, both of which make use of the island’s offshore waters. Data are
available on the taking of commercial fish species (particularly of tuna and billfish species),
though often these data derive from areas which extend beyond the 200 nm limit of the island’s
EEZ. Far less is known about pelagic, non-commercial fish populations (including sharks),
offshore cetaceans, benthic invertebrates and the deep-sea benthos in general.

Much of the fisheries data will have come from logbooks, which are known to be of dubious
accuracy.

A similar review of marine environmental knowledge was undertaken by the author in 2012 for
the Pitcairn Islands, another UK Overseas Territory in the South Pacific (Irving & Dawson,
2012). There was a similar lack of information available for much of the islands' offshore area
(extending to the 200 nm EEZ limit), with much more information being available for the
nearshore area, as has been the case with Ascension. The Pitcairn Islands also lie at the very
fringes of the range of tuna (yellowfin, bigeye, skipjack and albacore) and certain billfish (blue
and striped marlin), and there had been commercial fishing licenses sold to Korean and
Japanese fishing concerns in the past.

Given the lack of good quality, local data and an apparent dearth of knowledge overall, the
precautionary principle should be adopted wherever possible.
4.2
The marine biodiversity importance of Ascension’s offshore waters

The geographical location of the island, almost mid-way between the continental land masses
of West Africa and that of Brazil in South America, is largely responsible for the mix of species
which are present in its waters, some of which have origins on the west side and some on the
east side of the South Atlantic. Other physical factors which give rise to the unique set of
conditions which influence the island’s waters include the shifting location of influencing ocean
currents; the unusual bathymetry of the seabed and its proximity to the Mid-Atlantic Ridge and
associated deep-sea features; and the lack of reef-building corals surrounding a tropical island.

Those species of greatest conservation interest include the endemic Ascension frigatebird
(recently discovered to venture as far as the coast of West Africa on its foraging flights); a very
large sooty tern population; the second largest nesting population in the Atlantic of endangered
green turtles; a juvenile population of critically-endangered hawksbill turtles; a small, overwintering population of humpback whales; and a resident population of oceanic bottlenose
dolphins.

The Ascension Island EEZ features a number of prominent seamounts, the shallowest of which
rises to within 72 m of the surface. Seamounts are typically associated with increased densities
of marine life, particularly of sessile invertebrates (such as sponges and fan corals), and mobile
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The Offshore Marine Environment of Ascension Island, South Atlantic
echinoderms, molluscs and crustacea. The fish fauna will also be richer on the slopes of these
seamounts. Seamounts also have the ability to act as ‘stepping stones’, providing opportunities
for certain species to expand their ranges.
4.3
The main threats to maintaining and enhancing the offshore marine
biodiversity

Licensed commercial fishing by foreign vessels has been permitted to take place within the
island’s EEZ over recent years. Even though the island’s EEZ lies at the southern and western
edge of the main fishery area, catch returns have shown that considerable numbers of tuna
species and billfish species are extracted, together with certain oceanic shark species and
other species of lesser value to the vessel operators.

As well as the extraction of targeted species (typically of apex predators), a wide range of
species are caught incidentally as bycatch, including sharks and other non-target fish species
and, to a lesser extent, seabirds.

A recent paper (Paleczny et al., 2015) has shown a global decline in seabirds over the period
between 1950 and 2010 of 69.7%. The cause of the estimated overall decline in seabird
populations is likely to be a suite of threatening human activities, such as introduced species at
nesting colonies (e.g., rats, cats), entanglement in fishing gear at sea, pollution, direct
exploitation (harvesting chicks, eggs, adults) etc., with overfishing of food sources by humans
being one of the main categories.

A number of Ascension’s seabird species (particularly masked boobies and sooty terns) have
been shown to favour certain areas of the EEZ during their foraging flights from the island. It
has been postulated that these may be areas where there are concentrations of surface fish
species, possibly being driven to the surface by schools of tuna preying upon them too.
Continuous removal of tuna may well lead to these ‘hotspots’ being reduced in importance,
requiring the seabirds to expend greater amounts of energy seeking out suitable prey.
4.4
What would a no-take MPA protect and secure?

A no-take MPA would provide a ‘reference area’ in the tropical Atlantic Ocean, where no other
such reference area exists. Within this reference area, no commercial fishing would be
undertaken, and thus no extraction of apex predators. This would allow the ecosystem within
the EEZ to resort gradually to its non-fished, natural state.

A no-take MPA would ensure that seamounts could remain in a pristine condition, allowing their
unique marine life to continue to flourish. This assumes that they have not been subject to
commercial bottom fishing with nets (which would have adversely affected sessile faunal
communities) or to large-scale long-line or net fisheries (which could well have taken out many
of the apex predatory species).

A no-take MPA would prevent extractive operations other than fishing (such as deep sea
mining) from taking place.

A no-take MPA, extending from the 12 nm limit to the extent of the EEZ at 200 nm, would allow
for the continuation of sports fishing (sea angling) and for the extraction of other marine life
(such as spiny lobsters) from within the 12 nm limit. However, these activities require on-going
monitoring to ensure that over-exploitation does not result, particularly regarding the selective
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The Offshore Marine Environment of Ascension Island, South Atlantic
extraction of the largest individuals. It is reassuring to note that inshore fishing licensing is being
brought in by the AIG Conservation Department.
4.5
What are the main data gaps to fill?

It is clear from the findings of this Review that our knowledge of the offshore environment
around Ascension Island would benefit from further research studies (as indicated below).

In recent years, the development of tracking devices which can be fitted to animals without
apparent ill-effect or change in behaviour patterns has increased our knowledge of the range of
certain species dramatically. For the first time, we have been able to track an individual animal,
be it a seabird, turtle or cetacean, beyond the horizon and for days at a time as well. Our
understanding of how these animals utilize the offshore waters around the island would benefit
from many more such studies, especially in the case of the island’s seabirds, the three species
of turtle known to be present, various tuna species, humpback whales and even whale sharks
and other shark species.

The possible link between tuna populations (when near the surface) and the island’s seabird
populations is of great interest and would benefit from further research. Research into the
behaviour of tuna within Ascension Island’s EEZ would help to establish more precise
population movements, the timing of migrations, and whether more resident populations exist
that can be effectively protected at a local level.

Deep-sea researchers should be encouraged to look at the marine life inhabiting the numerous
seamounts and deep-sea trenches and canyons which are present within the EEZ and about
which we know very little.

Species identification – e.g. spotted dolphins Stenella spp.? Are these Atlantic spotted dolphins
or Pan-tropical spotted dolphins? Which species of petrels are present?

Humpback whales – can it be determined if they belong to Stock A (western South Atlantic) or
Stock B (eastern South Atlantic)? We would then know where they spend their summers. How
many individuals visit Ascension and are they the same individuals year on year? Does
Ascension act as a calving and nursery area for them?

Encouraging members of the local community to assist with tagging large game fish and shark
species, in order to determine their ranges.
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5. References
AIG, 2012. Ascension Island Conservation Quarterly. Issue 39 – July-September 2012. Available at:
http://www.ascension-island.gov.ac/wp-content/uploads/2012/12/ascension-island-conservationquarterly-issue-39.pdf
AIG, 2014. Shallow marine habitat action plan. In: The Ascension Island Biodiversity Action Plan.
Ascension Island Government Conservation Department, Georgetown, Ascension Island.
AIG, 2015a. Green turtle species action plan. In: The Ascension Island Biodiversity Action Plan.
Ascension Island Government Conservation Department, Georgetown, Ascension Island.
AIG, 2015b. Ascension Island frigate bird species action plan. In: The Ascension Island Biodiversity
Action Plan. Ascension Island Government Conservation Department, Georgetown, Ascension
Island.
AIG, 2015c. Masked booby species action plan. In: The Ascension Island Biodiversity Action Plan.
Ascension Island Government Conservation Department, Georgetown, Ascension Island.
AIG, 2015d. Sooty tern species action plan. In: The Ascension Island Biodiversity Action Plan.
Ascension Island Government Conservation Department, Georgetown, Ascension Island.
Allen, J.A. and Sanders, H.L., 1996. The zoogeography, diversity and origin of the deep-sea
protobranch bivalves of the Atlantic: the epilogue. Progress in Oceanography, 38: 95−153.
Almeida, A.D., Filgueiras, H., Braby, R. and Tiwari, M. 2014. Increasing evidence of leatherback
migrations from Brazilian beaches to the West African coastline. African Sea Turtle Newsletter, 1:
9-11.
Angel, A., Nel, R., Wanless, R.M., Mellet, B., Harris, L. and Wilson, I. 2014. Ecological risk assessment
of sea turtles to tuna fishing in the ICCAT region. Collective Volume of Scientific Papers ICCAT,
70: 2226–2259.
Appleby, T. 2015. Fisheries law in action: An exploration of legal pathways to a better managed marine
environment. DPhil, University of the West of England.
Armstrong, M.A. and Reeves, S.J. 2015. A review of fisheries management options for Ascension
Island waters, 2: Inshore Fisheries. Unpublished report commissioned by Ascension Island
Government and the UK Foreign & Commonwealth Office. Cefas contract report C6389.
Ashmole, N.P. 1963. The biology of the Wideawake or Sooty tern on Ascension Island. Ibis, 103(3):
297-364.
Ashmole, N.P., Ashmole, M.J. & Simmons, K.E.L. 1994. Seabird conservation and feral cats on
Ascension Island, South Atlantic. In: Seabirds on Islands: Threats, Case Studies and Action
Plans. BirdLife International, Cambridge, UK. pp. 94–121.
Au, D.W. and Pitman, R.L. 1988. Seabird relationships with tropical tunas and dolphins. In: Seabirds
and other marine vertebrates. Competition, predation and other interactions. (ed. J. Burger).
Colombia University Press, New York. pp. 174–212.
Baum, J., Myers, R., Kehler, D., Worm, B., Harley, S. and Doherty, P., 2003. Collapse and conservation
of shark populations in the Northwest Atlantic. Science 299 (17), 389–392.
Baum, J.K. and Myers, R.A. 2004. Shifting baselines and the decline of pelagic sharks in the Gulf of
Mexico. Ecology Letters. 7(3): 135–145.
Baum, J., Medina, E., Musick, J.A. & Smale, M. 2006. Carcharhinus longimanus. The IUCN Red List of
Threatened Species. Version 2015.2. <www.iucnredlist.org>.
Page 64 of 115
The Offshore Marine Environment of Ascension Island, South Atlantic
Baum, J., Clarke, S., Domingo, A., Ducrocq, M., Lamónaca, A.F., Gaibor, N., Graham, R., Jorgensen,
S., Kotas, J.E., Medina, E., Martinez-Ortiz, J., Monzini Taccone di Sitizano, J., Morales, M.R.,
Navarro, S.S., Pérez-Jiménez, J.C., Ruiz, C., Smith, W., Valenti, S.V. & Vooren, C.M. 2007.
Sphyrna lewini. The IUCN Red List of Threatened Species. Version 2015.1.
<www.iucnredlist.org>. Downloaded on 13 June 2015.
Bennett, M.B., Gordon, I. & Kyne, P.M. 2003. (SSG Australia & Oceania Regional Workshop, March
2003) Carcharhinus galapagensis. The IUCN Red List of Threatened Species. Version 2015.1.
<www.iucnredlist.org>. Downloaded on 11 June 2015.
BirdLife International, 2012. Fregata aquila. The IUCN Red List of Threatened Species. Version 2015.2.
<www.iucnredlist.org>.
Bourne, W.R.P and Simmons, K.E.L. 1998. Birds recorded within 200 nautical miles of Ascension. Sea
Swallow, 47: 42-56.
Broderick, A.C., Frauenstein, R., Glen, F., Hays, G.C., Jackson, A.L., Pelembe, T., Ruxton, G.D. and
Godley, B.J. 2006. Are green turtles globally endangered? Global Ecology and Biogeography,
15: 21–26.
Brown, J., Colling, A., Park, D., Phillips, J., Rothery, D. and Wright, J., 1989. Ocean Chemistry and
Deep-sea Sediments. Pergamon Press, Oxford.
Brickle, P., Brown, J., Brewin, P., Dimmlich, W., Arkhipkin, A., Laptikovsky, V., Kupper, F., Tsiamis, K.,
Van West, P., Morley, S.A., Browning, S. and Browning, S. 2013. Assessing Ascension Island's
shallow marine biodiversity. Darwin Initiative Overseas Territories Challenge Fund final report.
Clark, M.R. 2001. Are deepwater fisheries sustainable? The example of orange roughy. Fisheries
Research, 51:123–135.
Clark, M.R. and Koslow, J.A. 2007. Impacts of fisheries on seamounts. pp. 413–41. In: Pitcher TJ,
Morato T, Hart PJB, Clark MR, Haggan N, Santos RS, eds. 2007. Seamounts: Ecology, Fisheries
and Conservation, vol. 12. Oxford, UK: Blackwell. 527 pp.
Clark, M.R., Vinnichenko, V.I., Gordon, J.D.M., Beck-Bulat, G.Z., Kukharev, N.N. and Kakora, A.F.
2007. Large-scale distant-water trawl fisheries on seamounts. pp 361-399. In: Pitcher TJ, Morato
T, Hart PJB, Clark MR, Haggan N, Santos RS, eds. 2007. Seamounts: Ecology, Fisheries and
Conservation, vol. 12. Oxford, UK: Blackwell. 527 pp.
Clark, M.R., Rowden, A.A., Schlacher, T., Williams, A., Consalvey, M., Stocks, K.I., Rogers, A.D.,
O’Hara, T.D., White, M., Shank, T.M. and Hall-Spencer, J.M. 2010. The ecology of seamounts:
structure, function, and human impacts. Annual Review of Marine Science, 2: 253-278.
Coelho, R., Fernandez-Carvalho, J. and Santos, M.N. 2013. A review of fisheries within the ICCAT
convention area that interact with sea turtles. Collective Volume of Scientific Papers ICCAT, 69:
1788–1827.
Collette, B., Amorim, A.F., Boustany, A., Carpenter, K.E., de Oliveira Leite Jr., N., Di Natale, A., et al.
2011a. Thunnus thynnus. The IUCN Red List of Threatened Species. Version 2015.2.
<www.iucnredlist.org>.
Collette, B., Acero, A., Amorim, A.F., Boustany, A., Canales Ramirez, C., Cardenas, G., et al. 2011b.
Thunnus albacares. The IUCN Red List of Threatened Species. Version 2015.2.
<www.iucnredlist.org>.
Collette, B., Acero, A., Amorim, A.F., Boustany, A., Canales Ramirez, C., Cardenas, G., et al.. 2011c.
Thunnus alalunga. The IUCN Red List of Threatened Species. Version 2015.2.
<www.iucnredlist.org>.
Collette, B., Acero, A., Amorim, A.F., Boustany, A., Canales Ramirez, C., Cardenas, G., et al. 2011d.
Thunnus obesus. The IUCN Red List of Threatened Species. Version 2015.2.
<www.iucnredlist.org>
Page 65 of 115
The Offshore Marine Environment of Ascension Island, South Atlantic
Collette, B., Acero, A., Amorim, A.F., Bizsel, K., Boustany, A., Canales Ramirez, C., et al., 2011e.
Xiphias gladius. The IUCN Red List of Threatened Species. Version 2015.2.
<www.iucnredlist.org>
Collette, B., Fernandes, P. and Heessen, H. 2015. Thunnus alalunga. The IUCN Red List of
Threatened Species 2015: e.T21856A18208821.
Compagno, L.J.V. 1984. Sharks of the World: An annotated and illustrated catalogue of shark species
known to date. Food and Agriculture Organization of the United Nations. pp. 521–524, 555 – 61,
590.
Cook, S.F. & Compagno, L. J.V. 2005. Hexanchus griseus. The IUCN Red List of Threatened Species.
Version 2015.2. <www.iucnredlist.org>.
Croxall, J.P., Butchart, S.H.M., Lascelles, B., Stattersfield, A.J., Sullivan, B., Symes, A. and Taylor, P.
2012. Seabird conservation status, threats and priority actions: a global assessment. Bird
Conservation International, 22(1): 1-34.
Cullis-Suzuki, S. and Pauly, D. (2010) Failing the high seas: a global evaluation of regional fisheries
management organizations. Marine Policy 34, 1036–1042.
Dawson, T. 2015. The UK Government agrees to create the world’s largest marine reserve around the
Pitcairn Islands, a UK Overseas Territory in the South Pacific. Pacific Conservation Biology,
21(3).
De Forges, B.R., Koslow, J.A. and Poore, G.C.B. 2000. Diversity and endemism of the seamount fauna
in the south-west Pacific. Nature, 405: 944-947.
Dorward, D.F. 1962. Comparative biology of the white booby and the brown booby Sula spp. at
Ascension. Ibis, 103: 174–220.
Edwards, A.J. 1993. New records of fishes from the Bonaparte Seamount and Saint Helena Island,
South Atlantic. Journal of Natural History, 27: 493-503.
Edwards, A.J. and Lubbock, H.R. 1982. The shark population of Saint Paul's Rocks. Copeia 1982: 223225.
Edwards, A.J. and Glass, C.W. 1987. The fishes of St Helena Island, South Atlantic Ocean. II. The
pelagic fishes. Journal of Natural History, 21: 1367-1394.
Emery, K.O. and Uchupi, E., 1984. The Geology of the Atlantic Ocean. Springer, Berlin, 1050 pp., 2
volumes.
Faneros, G. & Arnold, F. 2003. Geomorphology of two seamounts offshore Ascension Island, South
Atlantic Ocean. Proceedings of Oceans 2003, 22-26 Sept. 2003. Vol. 1, 39-49. Publisher: IEEE.
Fishbase.org. 2012. All fishes of Ascension Island. (www.fishbase.org). Searches undertaken between
19 May 2015 and 12 June 2015. [See also Froese & Pauly, 2015].
Fossette, S., Witt, M.J., Miller, P., Nalovic, M.A., Albareda, D., Almeida, A.P., Broderick, A.C., ChaconChaverri, D., Coyne, M.S., Domingo, A., Eckert, S., Evans, D., Fallabrino, A., Ferraroli, S.,
Formia, A., Giffoni, B., Hays, G.C., Hughes, G., Kelle, L., Leslie, A., Lopez-Mendilaharsu, M.,
Luschi, P., Prosdocimi, L., Rodriguez-Heredia, S., Turny, A., Verhage, S. and Godley, B.J. 2014.
Pan-Atlantic analysis of the overlap of a highly migratory species, the leatherback turtle, with
pelagic longline fisheries. Proceedings of the Royal Society B: Biological Sciences, 281(1780):
20133065-20133065.
Froese, R. and Pauly, D. (eds.). 2015. FishBase. World Wide Web electronic publication. [See also
Fishbase.org. 2012 citation]
Gallo, B.M.G., Macedo, S., Giffoni, B. de B., Becker, J.H. and Barata, P.C.R. 2006. Sea turtle
conservation in Ubatuba, southeastern Brazil, a feeding area with incidental capture in coastal
fisheries. Chelonian Conservation and Biology, 5: 93–101.
Page 66 of 115
The Offshore Marine Environment of Ascension Island, South Atlantic
Genin, A. 2004. Bio-physical coupling in the formation of zooplankton and fish aggregations over abrupt
topographies. Journal of Marine Systematics, 50: 3-20.
Hall-Spencer, J.M., Rogers, A., Davies, J., Foggo, A. 2007. Historical deep-sea coral distribution on
seamount, oceanic island and continental shelf-slope habitats in the NE Atlantic. In Conservation
and Adaptive Management of Seamount and Deep-Sea Coral Ecosystems, ed. R.Y. George,
S.D. Cairns, pp. 324. Miami: Rosenstiel School of Marine and Atmospheric Science.
Hammerschlag, N., Broderick, A.C., Coker, J.W., Coyne, M.S., Dodd, M., Frick, M.G., Godfrey, M.H.,
Godley, B.J., Griffin, D.B., Hartog, K., Murphy, S.R., Murphy, T.M., Nelson, E.R., Williams, K.L.,
Witt, M.J. and Hawkes, L.A. 2015. Evaluating the landscape of fear between apex predatory
sharks and mobile sea turtles across a large dynamic seascape. Ecology. (Pre-publication copy
viewed).
Hammond, P.S., Bearzi, G., Bjørge, A., Forney, K.A., Karkzmarski, L., Kasuya, T., Perrin, W.F., Scott,
M.D., Wang, J.Y. , Wells, R.S. & Wilson, B. 2012. Tursiops truncatus. The IUCN Red List of
Threatened Species. Version 2015.1. <www.iucnredlist.org>.
Hansen, J. A., Given, H. K, and Berger, J. 1996. Earthquake activity near Ascension Island, as seen by
a combined seismic/hydrophone array. Geothermics, 25(4/5): 507-519.
Huang, H-W. 2011. Bycatch of high sea longline fisheries and measures taken by Taiwan. Marine
Policy, 5: 712-720.
Huang, H-W. 2013. Characteristics of sea turtle incidental catch of Taiwanese longline fisheries in the
Atlantic Ocean. Collective Volume of Scientific Papers ICCAT, 69(5): 2233-2238.
Huang, H-W., Chou, S.-C., Dai, J.-P. and Shiao, C.-H. 2009. Overview of Taiwanese observers
program for large scale tuna longline fisheries in Atlantic Ocean from 2002 to 2006. Collective
Volume of Scientific Papers ICCAT, 64(7): 2508-2517.
Hueter, R.E., Tyminski, J.P. and de la Parra, R. 2013. Horizontal movements, migration patterns, and
population structure of whale sharks in the Gulf of Mexico and northwestern Caribbean Sea.
PLoS ONE 8(8): e71883. doi:10.1371/journal.pone.0071883.
Hughes, B.J. 2014. Breeding and population ecology of sooty terns on Ascension Island. PhD Thesis.
University of Birmingham, Birmingham, UK.
Hughes, B.J., Martin, G.R. and Reynolds, S.J. 2012. Estimate of sooty tern Onychoprion fuscatus
population size following cat eradication on Ascension Island, central Atlantic. Bulletin of the
African Bird Club, 19: 166–171.
Hughes, B.J., Martin, G.R., Giles, A.D., Dickey, R.C. and Reynolds, S.J. 2015. Identification of an
assembly site for migratory and tropical seabirds in the South Atlantic Ocean. Global Ecology
and Conservation, 1-11. http://dx.doi.org/10.1016/j.gecco.2015.04.011.
ICCAT. 2009. Report for Biennial Period 2008-2009. International Commission for the Conservation of
the Atlantic Tuna (ICCAT) SCRS, Madrid, Spain.
ICCAT. 2014. Report for the Biennial period 2012-13, Part II (2013) Vol. 2, English version, SCRS.
ICCAT, Madrid, Spain.
Irving, R.A. 1989. A preliminary investigation of the sublittoral habitats and communities of Ascension
Island, South Atlantic. Progress in Underwater Science, 13: 67-78.
Irving, R.A. 2013. Ascension Island’s hermatypic but non reef-building corals. In: C. Sheppard (ed.)
Coral Reefs of the United Kingdom Overseas Territories. pp 213-222. Springer.
Jefferson, T. A. and Schiro, A. J. 1997. Distribution of cetaceans in the offshore Gulf of Mexico.
Mammal Review 27: 27-50.
Page 67 of 115
The Offshore Marine Environment of Ascension Island, South Atlantic
Joung, S.J., Liu, K.M., Liao, Y.Y. and Hsu, H.H. 2005. Observed by-catch of Taiwanese tuna longline
fishery in the South Atlantic Ocean. Journal of the Fisheries Society of Taiwan 32(1): 69-77.
Kner, R. and Steindacher, F. 1867. Neue fische aus dem Museum der Herren Joh. C. Godeffroy and
Sohn in Hamburg. Sitzungsberichte der Kaiserlichen Akademie der Wissenschaften.
Mathematisch-Naturwissenschftliche Classe 54: 356-395, pls. 1-5.
Koslow JA. 1997. Seamounts and the ecology of deep-sea fisheries. American Scientist, 85:168–176.
Levin, L.A. and Gooday, A. 2003. The deep Atlantic Ocean. Ecosystems of the deep oceans (Tyler,
P.A. ed.). 111-178. Amsterdam: New York: Elsevier.
Luiz, O.J. and Edwards, A.J. 2011. Extinction of a shark population in the Archipelago of Saint Paul’s
Rocks (equatorial Atlantic) inferred from the historical record. Biological Conservation, 144: 28732881.
Mead, J. G. 1989. Beaked whales of the genus Mesoplodon. In: S. H. Ridgway and R. Harrison (eds),
Handbook of marine mammals, Vol. 4: River dolphins and the larger toothed whales, pp. 349430. Academic Press.
Melo, P.A.M.C., Júnior, M. de M.,De Macêdo, S.J., Araujo, M. and Neumann-Leitão, S. 2014. Copepod
distribution and production in a Mid-Atlantic Ridge archipelago. Annals of the Brazilian Academy
of Sciences, 86(4): 1719-1733.
Monniot, C., 1979. Adaptations of benthic filtering animals to the scarcity of suspended particles in
water. Ambio Spec. Rep., 6: 73−74.
Morato, T., Varkey, D.A., Damaso, C., Machete, M., Santos, M., Prieto, R.. Santos, R.S. and Pitcher,
T.J. 2008. Evidence of a seamount effect on aggregating visitors. Marine Ecoogy Progress
Series, 357: 23–32.
Mortimer, J.A. and Portier, K.M. 1989. Reproductive homing and interesting behaviour of the green
turtle (Chelonia mydas) at Ascension Island, South Atlantic Ocean. Copeia, 1989: 962–977.
Mortimer, J.A. and Donnelly, M. 2008. Eretmochelys imbricata. The IUCN Red List of Threatened
Species. Version 2015.2. <www.iucnredlist.org>.
Muss, A., Robertson, D.R., Stepien, C.A., Wirtz, P. and Bowen, B.W. 2001. Phylogeography of
Ophioblennius: the role of ocean currents and geography in reef fish evolution. Evolution, 55(3):
561-572.
Naro-Maciel, E., Bondioli, A.C.V., Martin, M., de Padua Almeida, A., Baptistotte, C., Bellini, C.,
Marcovaldi, M.A., Santos, A.J.B. & Amato, G. 2012. The Interplay of Homing and Dispersal in
Green Turtles: A Focus on the Southwestern Atlantic. Journal of Heredity, 103: 792–805.
Nielson, D.L. and Sibbett, B.S., 1996, Geology of Ascension Island, south Atlantic Ocean: Geothermics,
25(4/5), 427-448.
O’Hara, T.D. 2007. Seamounts: Centres of endemism or species richness for ophiuroids? Global
Ecology and Biogeography, 16: 720–732.
Oppel, S., Beard, A., Fox, D., Mackley, E., Leat, E., Henry, L., Clingham, E., Fowler, N., Sim, J.,
Sommerfeld, J., Weber, N., Weber, S. and Bolton, M. 2015. Foraging distribution of a tropical
seabird supports Ashmole’s hypothesis of population regulation. Behavioral Ecology and
Sociobiology, 69(6): 915-926.
Paleczny, M., Hammill, E., Karpouzi, V. and Pauly, D. 2015. Population trend of the world’s monitored
seabirds, 1950-2010. PLoS ONE 10(6): e0129342. doi:10.1371/journal.pone.0129342.
Piontkovski, S.A. and Landry, M.R. 2003. Copepod species diversity and climate variability in the
tropical Atlantic Ocean. Fish Oceanography, 12: 352-359.
Page 68 of 115
The Offshore Marine Environment of Ascension Island, South Atlantic
Pitcher, T.J., Morato, T., Hart, P.J.B., Clark, M.R., Haggan, N., Santos, R.S, eds. 2007. Seamounts:
Ecology, Fisheries and Conservation, vol. 12. Oxford, UK: Blackwell. 527 pp.
Price, J.H. and John, D.M. 1980. Ascension Island: a survey of inshore benthic macroorganisms,
communities and interactions. Aquatic Botany, 9: 251-278.
Putman, N.F. and Naro-Maciel, E. 2013. Finding the ‘lost years’ in green turtles: insights from ocean
circulation models and genetic analysis. Proceedings of the Royal Society B 280: 20131468.
http://dx.doi.org/10.1098/rspb.2013.1468
Putman, N.F., Abreu-Grobois, F.A., Broderick, A.C., Ciofi, C., Formia, A., Godley, B.J., Stroud, S.,
Pelembe, T., Verley, P. and Williams, N. 2014. Numerical dispersal simulations and genetics help
explain the origin of hawksbill sea turtles in Ascension Island. Journal of Experimental Marine
Biology and Ecology, 450: 98–108.
Randall, J.E. 1992. Review of the biology of the tiger shark Galeocerdo cuvier. Australian Journal of
Marine and Freshwater Research 43: 21–31.
Ratcliffe, N., Bell, M., Pelembe, T., Boyle, D., Benjamin, R., White, R., Godley, B., Stevenson, J. and
Sanders, S. 2010. The eradication of feral cats from Ascension Island and its subsequent
recolonization by seabirds. Oryx, 44: 20.
Reeves, S.A. and Laptikovsky, V. 2014. A review of fisheries management options for Ascension Island
waters. 1: offshore fisheries. Unpublished report to Ascension Island Government and the
Foreign and Commonwealth Office. Cefas contract report C6389. Lowestoft, Suffolk. 133 pp.
Reilly, S.B., Bannister, J.L., Best, P.B., Brown, M., Brownell Jr., R.L., Butterworth, D.S., Clapham, P.J.,
Cooke, J., Donovan, G.P., Urbán, J. & Zerbini, A.N. 2008. Megaptera novaeangliae. The IUCN
Red List of Threatened Species. Version 2015.1. www.iucnredlist.org.
Roark, E.B., Guilderson, T.P., Dunbar, R.B. and Ingram, B.L. 2006. Radiocarbon-based ages and
growth rates of Hawaiian deep-sea corals. Marine Ecology Progress Series, 327:1–14.
Rogers, A.D., Baco, A., Griffiths, H., Hart, T., Hall-Spencer, J.M. 2007. Corals on seamounts. In:
Pitcher, T.J., Morato, T., Hart, P.J.B., Clark, M.R., Haggan, N. and Santos, R.S., (eds.) 2007.
Seamounts: Ecology, Fisheries and Conservation, vol. 12. Oxford, UK: Blackwell. 527 pp.
Rogers, A.D. (Ed.). 2013. The Global State of the Ocean; Interactions Between Stresses, Impacts and
Some Potential Solutions. Synthesis papers from the International Programme on the State of
the Ocean 2011 and 2012 Workshops. Marine Pollution Bulletin, 74(2): 491–552.
http://www.stateoftheocean.org/pdfs/IPSO-Papers-Combined-15.1.14.pdf
RSPB. 2014. Ascension Island Ocean Sanctuary – a unique opportunity to protect the tropical Atlantic.
Leaflet produced by the Royal Society for the Protection of Birds. Sandy, UK.
Sales, G., Giffoni, B.B. and Barata, P.C.R. 2008. Incidental catch of sea turtles by the Brazilian pelagic
longline fishery. Journal of the Marine Biological Association UK, 88: 853–864.
Samadi, S., Bottan, L., Macpherson, E., Richer de Forges, B. and Boisselier, M-C. 2006. Seamount
endemism questioned by the geographical distribution and population genetic structure of marine
invertebrates. Marine Biology, 149:1463–1475.
Samadi, S., Schlacher, T.A. and Richer de Forges, B. 2007. Seamount benthos. In: Pitcher, T.J.,
Morato, T., Hart, P.J.B., Clark, M.R., Haggan, N. and Santos, R.S., (eds.) 2007. Seamounts:
Ecology, Fisheries and Conservation, vol. 12. Oxford, UK: Blackwell. 527 pp.
Schreiber, R.W. and Clapp, R.B. 1987. Pelecaniform feeding ecology. In: Seabirds: feeding biology and
role in marine ecosystems (ed. J. P. Croxall). Cambridge University Press, Cambridge, UK. pp.
173–188.
Page 69 of 115
The Offshore Marine Environment of Ascension Island, South Atlantic
Scullion, J. 1990. Review of the fish resources, fisheries and oceanography within the Exclusive Fishing
Zone of Ascension Island. Report to the Overseas Development Administration (DFID) and the St
Helena Government. 77 pp.
Seminoff, J.A., 2004. Chelonia mydas. The IUCN Red List of Threatened Species. Version 2015.2.
<www.iucnredlist.org>.
Séret, B. 2005. Identification guide of the main shark and ray species of the eastern tropical Atlantic, for
the purpose of the fishery observers and biologists. FIBA, IUCN & PRCM.
Sheppard, C., Carr, P., Graham, N., Harris, A., Head, C., Koldewey, H., Meeuwig, J., Mortimer, J.,
Perkis, S., Price, A., Roberts, C., Schleyer, M. Sheppard, A., Tamelander, J. and Turner, J. 2012.
Conservation and Management in British Indian Ocean Territory (Chagos Archipelago).
Unpublished report. 28 pp.
Shirihai, H. and Jarrett, B. 2006. Whales, dolphins and seals: a field guide to the marine mammals of
the world. Bloomsbury, 272 pp.
Sibuet, M. 1979. Distribution and diversity of asteroids in Atlantic abyssal basins. Sarsia, 64: 85-91.
Simpfendorfer, C. 2009. Galeocerdo cuvier. The IUCN Red List of Threatened Species. Version 2015.2.
<www.iucnredlist.org>.
Stevens, J. 2009. Prionace glauca. The IUCN Red List of Threatened Species. Version 2015.2.
<www.iucnredlist.org>.
Stonehouse, B. and Stonehouse, S. 1963. The frigate bird Fregata aquila of Ascension Island. Ibis,
103: 409–422.
Taylor, B.L., Baird, R., Barlow, J., Dawson, S.M., Ford, J., Mead, J.G., Notarbartolo di Sciara, G.,
Wade, P. & Pitman, R.L. 2008a. Physeter macrocephalus. The IUCN Red List of Threatened
Species. Version 2015.1. <www.iucnredlist.org>.
Taylor, B.L., Baird, R., Barlow, J., Dawson, S.M., Ford, J., Mead, J.G., Notarbartolo di Sciara, G.,
Wade, P. & Pitman, R.L. 2008b. Mesoplodon europaeus. The IUCN Red List of Threatened
Species. Version 2015.2. <www.iucnredlist.org>
Thistle, D. 2003. The deep-sea floor: an overview. In: Ecosystems of the World 28, P. A. Tyler, editor.
Elsevier Science pp. 5-37.
Tomczac, M. and Godfrey, S. 1994. Regional oceanography: an introduction. Oxford, Elsevier Science
Ltd.
Tsiamis, K., Peters, A.F., Shewring, D.M., Asensi, A.O., Van West, P. and Küpper, F.C. 2014. Marine
benthic algal flora of Ascension Island, South Atlantic. Journal of the Marine Biological
Association of the United Kingdom, 1-8.
Trunov, I.A. 2006. Ichthyofauna of seamounts around the island of Ascension and St Helena Island.
Journal of Ichthyology, 46(7): 493-499.
van Andel, T.H., Rea, D.K., von Herzen, R.P and Hoskins, H. 1973. Ascension Fracture Zone,
Ascension Island and the Mid-Atlantic Ridge. Geological Society of America Bulletin, 84(5): 15271546.
Vaske, T.J., de Lima, K.L., Ribeiro, A.C.B. and Lessa, R.P. 2008. Record of the St Helena deep water
scorpionfish, Pontinus nigropunctatus (Günther) (Scorpaeniformes: Scorpaenidae) in the Saint
Peter and Saint Paul Archipelago, Brazil. Pan-American Journal of Aquatic Sciences, 3: 46-48.
Vinnichenko, V.I. 2002. Prospects of Fisheries on the Seamounts. ICES CM 2002/M32. ICES,
Copenhagen.
Page 70 of 115
The Offshore Marine Environment of Ascension Island, South Atlantic
Wallace, B.P., Kot, C.Y., DiMatteo, A.D., Lee, T., Crowder, L.B. and Lewison, R.L. 2013. Impacts of
fisheries bycatch on marine turtle populations worldwide: toward conservation and research
priorities. Ecosphere, 4: art40.
Wallbridge, G., Small, B. and McGowan, R.Y. 2003. From the Rarities Committee’s files: Ascension
Frigatebird on Tiree - new to the Western Palearctic. British Birds, 96: 58–73.
Ward, P. and Myers, R.A. 2005. Shifts in open-ocean fish communities coinciding with the
commencement of commercial fishing. Ecology, 86(4): 835-847.
Weber, S.B., Weber, N., Ellick, J., Avery, A., Godley, B.J., Sim, J., Williams, N. & Broderick, A.C.
2014a. Recovery of the South Atlantic’s largest green turtle nesting population. Biodiversity and
Conservation, 23: 3005–3018.
Weber, S.B., Weber, N., Godley, B.J., Pelembe, T., Stroud, S., Williams, N. and Broderick, A.C. 2014b.
Ascension Island as a mid-Atlantic developmental habitat for juvenile hawksbill turtles. Journal of
the Marine Biological Association of the UK.
Weimerskirch, H., Corre, M., Gadenne, H., Pinaud, D., Kato, A., Ropert-Coudert, Y. and Bost, C-A.
2009. Relationship between reversed sexual dimorphism, breeding investment and foraging
ecology in a pelagic seabird, the masked booby. Oecologia 161: 637–649.
Weir, C.R. and Pierce, G.J. 2013. A review of the human activities impacting cetaceans in the eastern
tropical Atlantic. Mammal Review, 43(4): 258-274.
Wilson, R. R. & Kaufmann, R. S. 1987. Seamount biota and biogeography. Geophysical Monographs,
43: 355–377.
Wirtz, P., Bingeman, J., Bingeman, J., Fricke, R., Hook, T.J. and Young, J. 2014. The fishes of
Ascension Island, central Atlantic Ocean - new records and an annotated check-list. Journal of
the Marine Biological Association of the United Kingdom, 1-16.
http://www.journals.cambridge.org/abstract_S0025315414001301
Witherington, B., Hirama, S. & Hardy, R. 2012. Young sea turtles of the pelagic Sargassum-dominated
drift community: habitat use, population density, and threats. Marine Ecology Progress Series,
463: 1–22.
Yeh, Y-M., Huang, H-W., Dietrich, K.S. and Melvin, E. 2013. Estimates of seabird incidental catch by
pelagic longline fisheries in the South Atlantic Ocean: Seabird bycatch in the South Atlantic
Ocean. Animal Conservation, 16: 141–152.
Page 71 of 115
The Offshore Marine Environment of Ascension Island, South Atlantic
6. Bibliography
Seabirds
Ascension Island Government. 2015. Ascension Island frigate bird species action plan. In: The Ascension Island
Biodiversity Action Plan. Ascension Island Government Conservation Department, Georgetown, Ascension
Island.
Ashmole, N.P. 1963. The biology of the Wideawake or Sooty tern on Ascension Island. Ibis, 103(3): 297—364.
Atkinson, P., Caddick, J. and Dowsett, R. 2010. Checklist of the birds of Ascension Island. Published by the African
Bird Club.
Avise, J.C., Nelson, W.S., Bowen, B.W. and Walker, D. 2000. Phylogeography of colonially nesting seabirds, with
special reference to global matrilineal patterns in the sooty tern (Sterna fuscata). Molecular Ecology, 9(11):
1783-1792.
Barrett, R.T., Camphuysen, K.C.J., Anker-Nilssen, T., Chardine, J.W., Furness, R.W., Garthe, S., Hüppop, O.,
Leopold, M.F., Montevecchi, W.A. and Veit, R.R. 2007. Diet studies of seabirds: a review and
recommendations. ICES Journal of Marine Science: Journal du Conseil, 64: 1675-1691.
BirdLife International, 2010. Marine Important Bird Areas toolkit: standardised techniques for indentifying priority
sites for the conservation of seabirds at sea. BirdLife International, Cambridge UK. Version 1.2: February
2011.
Bolton, M., Fowler, N., Hesketh, R., Kirby, W., Mackley, E., Ratcliffe, N., Reynolds, S.J., Sanders, S., Sim, J.,
Stringer, C., Stroud, S., Wade, D., Wearn, C.P., Williams, N. and Fisher, I. 2012. Ascension Island RSPB
Seabird Monitoring Manual.
Bourne, W.R.P and Simmons, K.E.L. 1998. Birds recorded within 200 nautical miles of Ascension. Sea Swallow,
47: 42-56.
Bourne, W.R.P and Simmons, K.E.L. 2001. The distribution and breeding success of seabirds on and around
Ascension in the tropical Atlantic Ocean. Atlantic Seabirds, 3(4): 187-202.
Bray, A., Hughes, B. J., Giles, A. and Wearn, C.P. 2012. Sooty Terns on Ascension Island, South Atlantic: Army
Ornithological Society Integrated Population Monitoring Programme 25th Report. Army Ornithological
Society (AOS).
Bugoni, L., Mancini, Pl., Monteiro, Ds., Nascimento, L. and Neves, Ts. 2008. Seabird bycatch in the Brazilian
pelagic longline fishery and a review of capture rates in the SW Atlantic. Endangered Species Research, 5:
137-147.
Camphuysen, C.J., Shamoun-Baranes, J., Bouten, W., Garthe, S., 2012. Identifying ecologically important marine
areas for seabirds using behavioural information in combination with distribution patterns. Biological
Conservation, 156: 22-29.
Costa, D.P., Breed, G.A. and Robinson, P.W. 2012. New insights into pelagic migrations: implications for ecology
and conservation. Annual Review of Ecology, Evolution, and Systematics, 43(1): 73-96.
Croxall, J.P., Butchart, S.H.M., Lascelles, B., Stattersfield, A.J., Sullivan, B., Symes, A. and Taylor, P. 2012.
Seabird conservation status, threats and priority actions: a global assessment. Bird Conservation
International, 22(1): 1-34.
Den Hartog, J.C. 1987. A record of red-footed booby from the Cape Verde Islands with a review of the status of this
species in the South Atlantic. Zoologische Mededelingen, 61: 40-419.
Dorward, D.F. 1962. Comparative biology of the white booby and the brown booby Sula spp. at Ascension. Ibis,
103: 174-220.
Dorward, D.F. 1963. The fairy tern Gygis alba on Ascension Island. Ibis, 103: 365-378.
Granadeiro, J.P., Phillips, R.A., Brickle, P. and Catry, P. 2011. Albatrosses following fishing vessels: how badly
hooked are they on an easy meal? PLoS ONE, 6(3): e17467.
Grecian, W.J., Witt, M.J., Attrill, M.J., Bearhop, S., Godley, B.J., Grémillet, D., Hamer, K.C., Votier, S.C., 2012. A
novel projection technique to identify important at-sea areas for seabird conservation: an example using
northern gannets breeding in the north east Atlantic. Biological Conservation, 156: 43-52.
Hebshi, A.J., Duffy, D.C. and Hyrenbach, K.D. 2008. Associations between seabirds and subsurface predators
around Oahu, Hawaii. Aquatic Biology, 19: 89-98.
Hilton, G.M. and Cuthbert, R.J. 2010. The catastrophic impact of invasive mammalian predators on birds of the UK
Overseas Territories: a review and synthesis. Ibis, 152: 443-458.
Page 72 of 115
The Offshore Marine Environment of Ascension Island, South Atlantic
Hughes, B. J. and Wearn, C. P. 2004. Sooty terns on Ascension Island, South Atlantic: Integrated population
monitoring programme. Army Ornithological Society Expedition, Report 15, Dec 2004.
Hughes, B.J. and Wearn, C.P. 2006. Longevity of sooty terns Sterna fuscata on Ascension Island. Atlantic
Seabirds, 7: 42-43.
Hughes, B.J., Martin, G.R. and Reynolds, S.J. 2010. Sooty terns Onychoprion fuscatus on Ascension Island in the
South Atlantic are a reproductively isolated population. Revista Brasileira de Ornitologia, 18(3): 194-198.
Hughes, B.J., Martin, G.R., Giles, A.D., Dickey, R.C. and Reynolds, S.J. 2015. Identification of an assembly site for
migratory and tropical seabirds in the South Atlantic Ocean. Global Ecology and Conservation, 1-11.
http://dx.doi.org/10.1016/j.gecco.2015.04.011.
Jones, H.P., Tershy, B.R., Zavaleta, E.S., Croll, D.A., Keitt, B.S., Finkelstein, M.E. and Howald, G.R. 2008.
Severity of the effects of invasive rats on seabirds - a global review. Conservation Biology, 22: 16-26.
Lascelles, B.G., Langham, G.M., Ronconi, R.A., Reid, J.B., 2012. From hotspots to site protection: identifying
marine protected areas for seabirds around the globe. Biological Conservation, 156: 5-14.
Le Corre, M., Jaeger, A., Pinet, P., Kappes, M.A., Weimerskirch, H., Catry, T., Ramos, J.A., Russell, J.C., Shah, N.
and Jaquemet, S. 2012. Tracking seabirds to identify potential Marine Protected Areas in the tropical
western Indian Ocean. Biological Conservation, 156: 83-93.
Ludynia, K., Kemper, J. and Roux, J-P. 2012. The Namibian Islands’ Marine Protected Area: Using seabird tracking
data to define boundaries and assess their adequacy. Biological Conservation, 156: 136-145.
Montevecchi, W.A., Hedd, A., McFarlane Tranquilla, L., Fifield, D.A., Burke, C.M., Regular, P.M., Davoren, G.K.,
Garthe, S., Robertson, G.J. and Phillips, R.A. 2012. Tracking seabirds to identify ecologically important and
high risk marine areas in the western North Atlantic. Biological Conservation, 156: 62-71.
Oppel, S., Beard, A., Fox, D., Mackley, E., Leat, E., Henry, L., Clingham, E., Fowler, N., Sim, J., Sommerfeld, J.,
Weber, N., Weber, S. and Bolton, M. 2015. Foraging distribution of a tropical seabird supports Ashmole’s
hypothesis of population regulation. Behavioral Ecology and Sociobiology, 69(6): 915-926.
http://link.springer.com/10.1007/s00265-015-1903-3
Ratcliffe, N. 2001. Monitoring methods for seabirds on Ascension Island. Report to RSPB.
Ratcliffe, N., Bell, M., Pelembe, T., Boyle, D., Benjamin, R., White, R., Godley, B., Stevenson, J. and Sanders, S.
2010. The eradication of feral cats from Ascension Island and its subsequent recolonization by seabirds.
Oryx, 44: 20.
http://www.journals.cambridge.org/abstract_S003060530999069X
Reynolds, S.J., Martin, G.R., Dawson, A., Wearn, C.P. and Hughes, B.J. 2014. The sub-annual breeding cycle of a
tropical seabird. PLoS ONE, 9: e93582.
http://dx.plos.org/10.1371/journal.pone.0093582
Ronconi, R.A., Lascelles, B.G., Langham, G.M., Reid, J.B. and Oro, D. 2012. The role of seabirds in Marine
Protected Area identification, delineation, and monitoring. Introduction and synthesis. Biological
Conservation, 156: 1-4.
Rowlands, B. 2001. Important bird areas in Ascension Island. In: Important bird areas in Africa and associated
islands: priority sites for conservation. Fishpool, L.D.C. and Evans, M.I. (eds.). Pisces Publications and
BirdLife International, Newbury & Cambridge, UK.
Scales, K. L., Miller, P. I., Embling, C. B., Ingram, S. N., Pirotta, E. and Votier, S.C. 2014. Mesoscale fronts as
foraging habitats: composite front mapping reveals oceanographic drivers of habitat use for a pelagic
seabird. Journal of The Royal Society Interface, 11(100): 20140679—20140679.
Simmons, K.E.L. 1967. Ecological adaptations in the life history of the brown booby at Ascension Island. Living
Bird, 6: 187—212.
Simmons, K.E.L. 1968. Occurrence and behaviour of the red-footed Booby at Ascension Island. Bulletin of the
British Ornithologists’ Club, 88: 15-20.
Soanes, L.M., Arnould, J.P.Y., Dodd, S.G., Sumner, M.D. and Green, J.A. 2013. How many seabirds do we need
to track to define home-range area? Journal of Applied Ecology, 50(3): 671-679.
http://onlinelibrary.wiley.com/doi/10.1111/1365-2664.12069/full
Sommerfeld, J., Kato, A., Ropert-Coudert, Y., Garthe, S., Wilcox, C. and Hindell, M.A. 2015. Flexible foraging
behaviour in a marine predator, the Masked booby (Sula dactylatra), according to foraging locations and
environmental conditions. Journal of Experimental Marine Biology and Ecology, 463: 79—86.
Spatz, D.R., Newton, K.M., Heinz, R., Tershy, B., Holmes, N.D., Butchart, S.H.M. and Croll, D.A. 2014. The
biogeography of globally threatened seabirds and island conservation opportunities: seabird conservation
opportunities. Conservation Biology.
http://doi.wiley.com/10.1111/cobi.12279
Page 73 of 115
The Offshore Marine Environment of Ascension Island, South Atlantic
Steeves, T.E., Anderson, D.J. and Friesen, V.L. 2005. A role for non-physical barriers to gene flow in the
diversification of masked boobies. Molecular Ecology, 12: 3877-3887. (http://doi.wiley.com/10.1111/j.1365294X.2005.02713.x)
Tasker, M.L., Camphuysen, C.J., Cooper, J., Garthe, S., Montevecchi, W.A. and Blaber, S.J.M. 2000. The impacts
of fishing on marine birds. ICES Journal of Marine Science: Journal du Conseil, 57(3): 531-547.
Tuck, G.N., Phillips, R.A., Small, C., Thomson, R.B., Klaer, N.L., Taylor, F., Wanless, R.M. and Arrizabalaga, H.
2011. An assessment of seabird-fishery interactions in the Atlantic Ocean. ICES Journal of Marine Science,
(8): 1628-1637.
http://icesjms.oxfordjournals.org/cgi/doi/10.1093/icesjms/fsr118
Uhlmann, S., Fletcher, D. and Moller, H. 2005. Estimating incidental takes of shearwaters in driftnet fisheries:
lessons for the conservation of seabirds. Biological Conservation, 123(2): 151-163.
Valle, S., Barros, N. and Wanless, R. M. 2014. Status and trends of the seabirds breeding at Tinhosa Grande
Island, Sao Tome & Principe. BirdLife International report, 27 pp.
Wallbridge, G., Small, B. and McGowan, R.Y. 2003. From the Rarities Committee's files: Ascension Frigatebird on
Tiree - new to the Western Palearctic. British Birds, 96: 58-73.
Weimerskirch, H., Chastel, O., Barbraud, C. and Tostain, O. 2003. Frigatebirds ride high on thermals. Nature,
421(6921): 333-334.
Weimerskirch, H., Corre, M., Gadenne, H., Pinaud, D., Kato, A., Ropert-Coudert, Y. and Bost, C-A. 2009.
Relationship between reversed sexual dimorphism, breeding investment and foraging ecology in a pelagic
seabird, the masked booby. Oecologia, 161(3): 637-649.
Weimerskirch, H., Corre, M.L, Kai, E.T. and Marsac, F. 2010. Foraging movements of great frigatebirds from
Aldabra Island. Relationship with environmental variables and interactions with fisheries. Progress in
Oceanography, 1-2: 204-213.
Wilkins, G.H. 1923. Report on birds collected during the voyage of the 'Quest' (Shackleton-Rowett Expedition) to
the Southern Atlantic. Ibis, 65(3): 474-510.
Turtles
Ackerman, R. A. 1977. The respiratory gas exchange of sea turtle nests. Respiration physiology, 1: 19-38.
Akesson, S., Luschi, P., Broderick, A. C., Glen, F., Godley, B. J., Papi, F. and Hays, G. C. 2001. Oceanic longdistance navigation: do experienced migrants use the earth’s magnetic field? The Journal of Navigation, 54:
419-427.
Akesson, S., Broderick, A.C., Glen, F., Godley, B.J., Luschi, P., Papi, F. and Hays, G.C. 2003. Navigation by green
turtles: which strategy do displaced adults use to find Ascension Island? Oikos, 103(2): 363-372.
Álvarez de Quevedo, I., San Félix, M. and Cardona, L. 2014. Temporal trends in the by-catch of loggerhead turtles
Caretta caretta in the Mediterranean Sea. Marine Ecology Progress Series, 504: 303-304.
Angel, A., Nel, R., Wanless, R.M., Mellet, B., Harris, L. and Wilson, I. 2014. Ecological risk assessment of sea
turtles to tuna fishing in the ICCAT region. Collective Volume of Scientific Papers ICCAT, 70(5): 2226-2259.
Anon. 1974. The turtle and the spreading sea floor. Science News, 105(21): 334.
Antworth, R. L., Pike, D. A. and Stiner, J. C. 2006. Nesting ecology current status and conservation of sea turtles in
Florida. Biological Conservation, 1: 10-15.
Báez, J.C., García Barcelona, S., Real, R. and Macías, D. 2014. Estimating by-catch of loggerhead turtles in the
Mediterranean - comment on Alvarez de Quevedo. Marine Ecology Progress Series, 504: 301-302.
Barceló, C., Domingo, A., Miller, P., Ortega, L., Giffoni, B., Sales, G., McNaughton, L., Marcovaldi, M., Heppell, S.
and Swimmer, Y. 2013. High use areas, seasonal movements and dive patterns of juvenile loggerhead sea
turtles in the SW Atlantic. Marine Ecology Progress Series, 479: 235-250.
Bass, A.L. 2006. Green turtle (Chelonia mydas) foraging and nesting aggregations in the Caribbean and Atlantic:
impact of currents and behavior on dispersal. Journal of Heredity, 97(4): 346-354.
Baudouin, M., de Thoisy, B., Chambault, P., Berzins, R., Entraygues, M., Kelle, L. Turny, A., Le Maho, Y. and
Chevallier, D. 2015. Identification of key marine areas for conservation based on satellite tracking of postnesting migrating green turtles. Biological Conservation, 36-41.
Bjorndal, K.A. 1980. Nutrition and grazing behaviour of the green turtle. Marine Biology, Volume 56, Issue 2: pp
147-154.
Page 74 of 115
The Offshore Marine Environment of Ascension Island, South Atlantic
Blumenthal, J.M., Abreu-Grobois, F.A., Austin, T.J., Broderick, A.C., Bruford, M.W., Coyne, M. S., Ebanks-Petrie,
G., Formia, A., Meylan, P.A., Meylan, A.B. and Godley, B.J. 2009. Turtle groups or turtle soup - dispersal
patterns of hawksbill turtles in the Caribbean. Molecular Ecology, 18(23): 4841-4853.
Bowen, B.W., Meylan, A.B. and Avise, J.C. 1989. The odyssey of the green turtle - Ascension Island revisited.
Proceedings of the National Academy of Sciences, 2: 573-576.
Brown, C.W. 1990. The Significance of the South Atlantic Equatorial Countercurrent to the Ecology of the Green
Turtle Breeding Population of Ascension Island. Journal of Herpetology, 24: 81-84.
Carr, A. 1980. Some problems of sea turtle ecology. American Zoologist, 20: 489-498.
Carr, A. and Hirth, H. 1961. Social facilitation in green turtle hatchlings. Animal Behaviour, 1: 68-70.
Carr, A., Ross, P. and Carr, S. 1974. Internesting behavior of the Green Turtle, Chelonia mydas, at a Mid-Ocean
Island Breeding Ground. Copeia, 3: 703.
Carranza, A., Domingo, A. and Estrades, A. 2006. Pelagic longlines a threat to sea turtles in the Equatorial Eastern
Atlantic. Biological Conservation, 131: 52-57.
Casale, P. and Mariani, P. 2014. The first ‘lost year’ of Mediterranean sea turtles: dispersal patterns indicate
subregional management units for conservation. Marine Ecology Progress Series, 498: 263-274.
Catry, P., Barbosa, C., Paris, B., Indjai, B., Almeida, A., Limoges, B., Silva, C. and Pereira, H. 2009. Status and
conservation of sea turtles in Guinea Bissau. Chelonian Conservation and Biology, 8(2): 150-160.
Christens, E. 1990. Nest emergence lag in loggerhead sea turtles. Journal of Herpetology, 4: 400-402.
Feagin, R.A., Sherman, D.J. and Grant, W.E. 2005. Coastal erosion, global sea level rise and the loss of sand
dune plant habitats. Frontiers in Ecology and the Environment, 3: 359.
Feazel, C.T. 1980. The turtle run from Ascension to Brazil and back. Sea Frontiers, 26: 240-243.
Fiedler, F.N., Sales, G., Giffoni, B.B., Monteiro-Filho, E.L.A., Secchi, E.R. and Bugoni, L. 2012. Driftnet fishery
threatens sea turtles in the Atlantic Ocean. Biodiversity and Conservation, 21(4): 915-931.
Fossette, S., Witt, M.J., Miller, P., Nalovic, M.A., Albareda, D., Almeida, A.P., Broderick, A.C., Chacon-Chaverri, D.,
Coyne, M.S., Domingo, A., Eckert, S., Evans, D., Fallabrino, A., Ferraroli, S., Formia, A., Giffoni, B., Hays,
G.C., Hughes, G., Kelle, L., Leslie, A., Lopez-Mendilaharsu, M., Luschi, P., Prosdocimi, L., RodriguezHeredia, S., Turny, A., Verhage, S. and Godley, B.J. 2014. Pan-Atlantic analysis of the overlap of a highly
migratory species, the leatherback turtle, with pelagic longline fisheries. Proceedings of the Royal Society B:
Biological Sciences, 281(1780): 20133065-20133065.
Gallo, B.M.G., Macedo, S., Giffoni, B. de B., Becker, J.H. and Barata, P.C.R. 2006. Sea turtle conservation in
southeastern Brazil - a feeding area with incidental capture in coastal fisheries. Chelonian Conservation and
Biology, 5: 93-101.
Godley, B. and Broderick, A.C. 2013. Are we getting into hot water? [Abstract = A short musing on the increasing
sea temperatures around Ascension Island and its likely biological impacts].
González C.V., Acha, E.M., Maxwell, S.M., Albareda, D., Campagna, C. and Mianzan, H. 2014. Young green
turtles, Chelonia mydas, exposed to plastic in a frontal area of the SW Atlantic. Marine Pollution Bulletin,
78(1-2): 56-62.
Hamann, M., Godfrey, M.H., Seminoff, J.A., Arthur, K. Barata, P.C.R., Bjorndal, K.A., Bolten, A.B., Broderick, A.C.,
Campbell, L.M., Carreras, C., Casale, P., Chaloupka, M., Chan, S.K.F., Coyne, M.S., Crowder, L.B., Diez,
C.E., Dutton, P.H., Epperly, S.P., FitzSimmons, N.N., Formia, A., Girondot, M., Hays, G.C., Cheng, I.S.,
Kaska, Y., Lewison, R., Mortimer, J.A., Nichols, W.J., Reina, R.D., Shanker, K., Spotila, J.R., Tomás, J.,
Wallace, B.P., Work, T.M., Zbinden, J. and Godley, B.J. 2010. Global research priorities for sea turtles in
the 21st century. Endangered Species Research, 11(3): 245-269.
Hamner, W.M. 1988. The 'lost year' of the sea turtle. Trends in Ecology & Evolution, 3(5): 116-118.
Hays, G.C., Akesson, S., Broderick, A.C., Glen, F., Godley, B.J., Luschi, P., Martin, C., Metcalfe, J.D. and Papi, F.
2001. The diving behaviour of green turtles undertaking oceanic migration to and from Ascension Island:
dive durations, dive profiles and depth distribution. Journal of Experimental Biology, 204(23): 4093-4098.
Hays, G.C., Dray, M., Quaife, T., Smyth, T.J., Mironnet, N.C., Luschi, P., Papi, F. and Barnsley, M.J. 2001.
Movements of migrating green turtles in relation to AVHRR derived sea surface temperature. International
Journal of Remote Sensing, 22(8): 1403-1411.
Hays, G.C., Broderick, A.C., Glen, F. and Godley, B.J. 2002. Change in body mass associated with long-term
fasting in a marine reptile: the case of green turtles (Chelonia mydas) at Ascension Island. Canadian
Journal of Zoology, 80(7): 1299-1302.
Hays, G.C., Akesson, S., Broderick, A.C., Glen, F., and Godley, B.J., Papi, F. and Luschi, P. 2003. Island-finding
ability of marine turtles. Proceedings of the Royal Society B: Biological Sciences, 270: S5--S7.
Page 75 of 115
The Offshore Marine Environment of Ascension Island, South Atlantic
Hays, G.C., Mortimer, J.A., Ierodiaconou, D. and Esteban, N. 2012. Use of long-distance migration patterns of an
endangered species to inform conservation planning for the world's largest marine protected area.
Conservation Biology, 6: 1636-1644.
Honig, M.B., Petersen, S.L. and Duarte, A. 2008. Turtle by-catch in longline fisheries operating within the Benguela
current large marine ecosystem. Collective Volume of Scientific Papers ICCAT, 62(6): 1757-1769.
Huxley, R. C. 1999. Historical overview of marine turtle exploitation, Ascension Island, South Atlantic. Marine Turtle
Newsletter, 84: 7-9.
León, Y.M. and Bjorndal, K.A. 2002. Selective feeding in the hawksbill turtle, an important predator in coral reef
ecosystems. Marine Ecology Progress Series, 245: 249-258.
Lohmann, Kenneth J. and Luschi, P. and Hays, G. C. 2008. Goal navigation and island-finding in sea turtles.
Journal of Experimental Marine Biology and Ecology, 356: 83-95.
Luschi, P., Hays, G.C., Del Seppia, C., Marsh, R. and Papi, F. 1998. The navigational feats of green sea turtles
migrating from Ascension Island investigated by satellite telemetry. Proceedings of the Royal Society of
London. Series B: Biological Sciences, 265: 2279-2284.
Luschi, P., Akesson, S., Broderick, A., Glen, F., Godley, B., Papi, F. and Hays, G. 2001. Testing the navigational
abilities of ocean migrants: displacement experiments on green sea turtles (Chelonia mydas). Behavioral
Ecology and Sociobiology, 50(6): 528-534.
Luschi, P., Hays, G.C. and Papi, F. 2003. A review of long-distance movements by marine turtles, and the possible
role of ocean currents. Oikos, 103: 293-302.
Mansfield, K. L., Wyneken, J., Porter, W.P. and Luo, J. 2014. First satellite tracks of neonate sea turtles redefine
the 'lost years' oceanic niche. Proceedings of the Royal Society B: Biological Sciences, 281(1781):
20133039.
Marcovaldi, M.A., Lopez, G.G., Soares, L.S., Santos, A.J.B., Bellini, C. and Barata, P.C.R. 2007. Fifteen years of
hawksbill sea turtle (Eretmochelys imbricata) nesting in northern Brazil. Chelonian Conservation and
Biology, 6(2): 223-228.
Marcovaldi, M.A., Lopez, G.G., Soares, L.S. and López-Mendilaharsu, M. 2012. Satellite tracking of hawksbill
turtles Eretmochelys imbricata nesting in northern Bahia, Brazil: turtle movements and foraging destinations.
Endangered Species Research, 17(2): 123-132.
McLellan, E., Arps, E., Donnelly, M. and Leslie, A. 2012. WWF Global Marine Turtle Strategy, 2012-2020. Gland,
Switzerland.
Meylan, A.B. and Donnelly, M. 1999. Status justification for listing the hawksbill turtle (Eretmochelys imbricata) as
critically endangered on the 1996 IUCN Red List of Threatened Animals. Chelonian Conservation and
Biology, 3(2): 200-224.
Meylan, P.A., Meylan, A.B. and Gray, J.A. 2011.2012. The ecology and migrations of sea turtles. 8. Tests of the
developmental habitat hypothesis. Bulletin of the American Museum of Natural History, 357: 1-70.
Moll, D. 1983. A Proposed origin of nesting Location Divergence and a shared feeding range in Brazilian Green
Turtle Populations. Copeia, 1: 121-125.
Monzón-Argüello, C., Rico, C., Marco, A., López, P. and López-Jurado, L.F. 2010. Genetic characterization of
eastern Atlantic hawksbill turtles at a foraging group indicates major undiscovered nesting populations in the
region. Journal of Experimental Marine Biology and Ecology, 387(1-2): 9-14.
Monzon-Arguello, C., Lopez-Jurado, L.F., Rico, C., Marco, A., Lopez, P., Hays, G.C. and Lee, P.L.M. 2010.
Evidence from genetic and Lagrangian drifter data for transatlantic transport of small juvenile green turtles.
Journal of Biogeography, 37: 1752-1766.
Monzón-Argüello, C., Loureiro, N.S., Delgado, C., Marco, A., Lopes, J.M., Gomes, M.G. and Abreu-Grobois, F.A.
2011. Príncipe island hawksbills: Genetic isolation of an eastern Atlantic stock. Journal of Experimental
Marine Biology and Ecology, 407(2): 345-354.
Mortimer, J.A. 1981. Reproductive ecology of the green turtle Chelonia mydas at Ascension Island. PhD thesis,
University of Florida.
Mortimer, J.A. and Carr, A. 1984. Reproductive ecology and behaviour of the green turtle at Ascension Island.
Research reports - National Geographic Society, 17: 257-270.
Mortimer, J.A. and Carr, A. 1987. Reproduction and migrations of the Ascension Island green turtle. Copeia, (1):
103-113.
Naro-Maciel, E., Bondioli, A.C.V., Martin, M., de Padua Almeida, A., Baptistotte, C., Bellini, C., Marcovaldi, M.A.,
Santos, A.J.B. and Amato, G. 2012. The interplay of homing and dispersal in green turtles of the South
West Atlantic. Journal of Heredity, 103(6): 792-805.
Papi, F., Luschi, P., Akesson, S., Capogrossi, S. and Hays, G.C. 2000. Open-sea migration of magnetically
disturbed sea turtles. Journal of Experimental Biology, 203: 3435-3443.
Page 76 of 115
The Offshore Marine Environment of Ascension Island, South Atlantic
Pooley, C. 2005. Temporal variation in spatial nesting patterns of green turtles at Ascension Island. MSc Thesis,
University of Exeter, UK.
Proietti, M.C., Lara-Ruiz, P., Reisser, J.W., Pinto, L. da S., Dellagostin, O.A. and Marins, L.F. 2009. Green turtles
foraging at Arvoredo Island in Southern Brazil Genetic characterization and mixed stock analysis through
mtDNA control region haplotypes. Genetics and Molecular Biology, 32(3): 613-618.
Proietti, M.C, Reisser, J.W., Kinas, P.G., Kerr, R., Monteiro, D.S., Marins, L.F. and Secchi, E.R. 2012. Green turtle
Chelonia mydas mixed stocks in the western South Atlantic, as revealed by mtDNA haplotypes and drifter
trajectories. Marine Ecology Progress Series, 447: 195-209. http://www.intres.com/abstracts/meps/v447/p195-209.
Putman, N.F. and Naro-Maciel, E. 2013. Finding the 'lost years' in green turtles: insights from ocean circulation
models and genetic analysis. Proceedings of the Royal Society B: Biological Sciences, 280(1768),
20131468-20131468.
Putman, N.F., Abreu-Grobois, F.A., Broderick, A.C., Ciofi, C., Formia, A., Godley, B.J., Stroud, S., Pelembe, T.,
Verley, P. and Williams, N. 2014. Numerical dispersal simulations and genetics help explain the origin of
hawksbill sea turtles in Ascension Island. Journal of Experimental Marine Biology and Ecology, 450: 98-108.
Reece, J.S., Castoe, T.A. and Parkinson, C.L. 2005. Historical perspectives on population genetics and
conservation of three marine turtle species. Conservation Genetics, 6: 235-251.
Roberts, M. A., Schwartz, T. S. and Karl, S. A. 2004. Global Population Genetic Structure and Male-Mediated
Gene Flow in the Green Sea Turtle - Analysis of Microsatellite Loci. Genetics, 4: 1857—1870.
Sales, G., Giffoni, B.B. and Barata, P.C.R. 2008. Incidental catch of sea turtles by the Brazilian pelagic longline
fishery. Journal of the Marine Biological Association UK, 88(4): 853-864.
Scott, R., Hodgson, D.J., Witt, M,J., Coyne, M.S., Adnyana, W., Blumenthal, J.M., Broderick, A.C., Canbolat, A.F.,
Catry, P., Ciccione, S., Delcroix, E., Hitipeuw, C., Luschi, P., Pet-Soede, L., Pendoley, K., Richardson, P.B.,
Rees, A.F. and Godley, B.J. 2012. Global analysis of satellite tracking data shows that adult green turtles
are significantly aggregated in Marine Protected Areas. Global Ecology and Biogeography, 11: 1053-1061.
http://doi.wiley.com/10.1111/j.1466-8238.2011.00757.x.
Swimmer, Y., Empey Campora, C., Mcnaughton, L., Musyl, M. and Parga, M. 2014. Post-release mortality
estimates of loggerhead sea turtles (Caretta caretta) caught in pelagic longline fisheries based on satellite
data and hooking location. Aquatic Conservation: Marine and Freshwater Ecosystems, 24(4): 498-510.
Tomás, J., Godley, B.J., Castroviejo, J. and Raga, J.A. 2010. Bioko - critically important nesting habitat for green
turtles in West Africa. Biodiversity and Conservation, 19(9): 2699—2714.
Vélez-Rubio, G.M., Estrades, A., Fallabrino, A. and Tomás, J. 2013. Marine turtle threats in Uruguay - insights from
12 years of stranding data. Marine Biology, 160(11): 2797-2811.
Walker, M.M., Dennis, T.E. and Kirschvink, J.L. 2002. The magnetic sense and its use in long-distance navigation
by animals. Current Opinion in Neurobiology, 6: 735-744.
Wallace, B.P., DiMatteo, A.D., Hurley, B.J., Finkbeiner, E.M., Bolten, A.B., Chaloupka, M.Y., Hutchinson, B.J.,
Abreu-Grobois, F.A., Amorocho, D., Bjorndal, K.A., Bourjea, J., Bowen, B.W., Dueñas, R.B., Casale, P.,
Choudhury, B.C., Costa, A., Dutton, P.H., Fallabrino, A., Girard, A., Girondot, M., Godfrey, M.H., Hamann,
M., López-Mendilaharsu, M., Marcovaldi, M.A., Mortimer, J.A., Musick, J.A., Nel, R., Pilcher, N.J., Seminoff,
J.A., Troëng, S., Witherington, B. and Mast, R.B. 2010. Regional Management Units for Marine Turtles: a
novel framework for prioritizing conservation and research across multiple scales. PLoS ONE, 5(12):
e15465.
http://dx.plos.org/10.1371/journal.pone.0015465
Wallace, B.P., Kot, C.Y., DiMatteo, A.D., Lee, T., Crowder, L.B. and Lewison, R.L. 2013. Impacts of fisheries
bycatch on marine turtle populations worldwide: toward conservation and research priorities. Ecosphere,
4(3): art40.
http://www.esajournals.org/doi/abs/10.1890/ES12-00388.1
Weber, N., Weber, S.B., Godley, B.J., Ellick, J., Witt, M. and Broderick, A.C. 2013. Telemetry as a tool for
improving estimates of marine turtle abundance. Biological Conservation, 167: 90-96.
Weber, S. B., Weber, N., Ellick, J., Avery, A., Godley, B.J., Sim, J., Williams, N. and Broderick, A.C. 2014.
Recovery of the South Atlantic's largest green turtle nesting population. Biodiversity and Conservation, 23:
3005-3018.
Weber, S.B., Weber, N., Godley, B.J., Pelembe, T., Stroud, S., Williams, N. and Broderick, A.C. 2014. Ascension
Island as a mid-Atlantic developmental habitat for juvenile hawksbill turtles. Journal of the Marine Biological
Association of the UK.
Witherington, B., Hirama, S and Hardy, R. 2012. Young sea turtles of the Sargassum-dominated pelagic drift
community. Marine Ecology Progress Series, 463: 1-22.
Witt, M.J., Augowet Bonguno, E., Broderick, A.C., Coyne, M.S., Formia, A., Gibudi, A., Mounguengui, G.A.,
Moussounda, C., NSafou, M., Nougessono, S., Parnell, R.J., Sounguet, G.P., Verhage, S. and Godley, B.J.
Page 77 of 115
The Offshore Marine Environment of Ascension Island, South Atlantic
2011. Tracking leatherback turtles from the world's largest rookery: assessing threats across the South
Atlantic. Proceedings of the Royal Society B: Biological Sciences, 278(1716): 2338-2347.
Fishes
Almada, V.C., Oliviera, R.F., Goncalves, E.J., Almeida, A.J., Santos, R.S and Wirtz, P. 2001. Patterns of diversity
of the north-eastern Atlantic blenniid fish fauna (Pisces: Blenniidae). Global Ecology & Biogeography, 10:
411-422.
Baum, J., Clarke, S., Domingo, A., Ducrocq, M., Lamónaca, A.F., Gaibor, N., Graham, R., Jorgensen, S., Kotas,
J.E., Medina, E., Martinez-Ortiz, J., Monzini Taccone di Sitizano, J., Morales, M.R., Navarro, S.S., PérezJiménez, J.C., Ruiz, C., Smith, W., Valenti, S.V. & Vooren, C.M. 2007. Sphyrna lewini. The IUCN Red List
of Threatened Species. Version 2015.1. <www.iucnredlist.org>. Downloaded on 13 June 2015.
Bennett, M.B., Gordon, I. & Kyne, P.M. 2003. (SSG Australia & Oceania Regional Workshop, March 2003)
Carcharhinus galapagensis. The IUCN Red List of Threatened Species. Version 2015.1.
<www.iucnredlist.org>. Downloaded on 11 June 2015.
Bowen, B.W., Bass, A.L., Muss, A., Carlin, J. and Robertson, D.R. 2006. Phylogeography of two Atlantic
squirrelfishes (Family Holocentridae): exploring links between pelagic larval duration and population
connectivity. Marine Biology, 149(4): 899-913.
Camhi, M., Pikitch, E.K. and Babcock, E.A. 2008. Sharks of the open ocean: biology, fisheries and conservation.
Blackwell Science. Oxford; Amies, Iowa. isbn = 9780632059959 0632059958.
Castro, J.J., Santiago, J.A. and Santana-Ortega, A.T. 2002. A general theory on fish aggregation to floating
objects: An alternative to the meeting point hypothesis. Reviews in Fish Biology and Fisheries, 11(3): 255277.
Edwards, A.J. 1993. New records of fishes from the Bonaparte Seamount and Saint Helena Island, South Atlantic.
Journal of Natural History, 27: 493-503.
Edwards, A.J. and Lubbock, H.R. 1982. The shark population of Saint Paul's Rocks. Copeia 1982: 223-225.
Edwards, A.J. and Glass, C.W. 1987. The fishes of St Helena Island, South Atlantic Ocean. II. The pelagic fishes.
Journal of Natural History, 21: 1367-1394.
Eschmeyer, W.N. 1971. Two new Atlantic Scorpionfishes. Proceedings of the California Academy of Science,
37(17): 501-507.
Fishbase.org. 2012. All fishes of Ascension Island. (www.fishbase.org)
Floeter, S.R. and Gasparini, J.L. 2000. Southwestern Atlantic reef fish fauna: composition and zoogeographic
patterns. Journal of Fish Biology, 56: 1099-1114.
Floeter, S.R., Rocha, L.A., Robertson, D.R., Joyeux, J.C., Smith-Vaniz, W.F., Wirtz, P., Edwards, A.J., Barreiros,
J.P., Ferreira, C.E.L, Gasparini, J.L., Brito, A., Falcon, J.M., Bowen, B.W. and Bernardi, G. 2008. Atlantic
reef fish biogeography and evolution. Journal of Biogeography, 35(1): 22-47.
Gomon, M.F. and Lubbock, R. 1980. A new hogfish of the genus Bodianus (Teleostei Labridae) from islands of the
Mid-Atlantic. Northeast Gulf Science, 3(2): 104-111.
Grey, M. 1953. Fishes of the family Gempylidae, with records of Nesiarchus and Epinnula from the western Atlantic
and descriptions of two new subspecies of Epinnula orientalis. Copeia, 135-141.
Handwerk, B. 2013. Secrets of whale shark migration revealed. National Geographic website.
http://news.nationalgeographic.com/news/2013/08/130821-whale-shark-satellite-tracking-migration-gulfmexico-science/
Hueter, R.E., Tyminski, J.P. and de la Parra, R. 2013. Horizontal movements, migration patterns, and population
structure of whale sharks in the Gulf of Mexico and northwestern Caribbean Sea. PLoS ONE 8(8): e71883.
doi:10.1371/journal.pone.0071883.
Kerstetter, D.W., Orbesen, E.S., Snodgrass, D. and Prince, E.D. 2009. Movements and habitat utilization of two
longbill spearfish in the Eastern tropical South Atlantic. Bulletin of Marine Science, 85: 173-182.
Kline, R.J., Khan, I.A. and Holt, G.J. 2011. Behavior, color change and time for sexual inversion in the protogynous
grouper (Epinephelus adscensionis). PLoS ONE, 6(5): e19576.
http://dx.plos.org/10.1371/journal.pone.0019576
Lewison, R.L., Freeman, S.A. and Crowder, L.B. 2004. Quantifying the effects of fisheries on threatened species:
the impact of pelagic longlines on loggerhead and leatherback sea turtles: fisheries effects on sea turtles.
Ecology Letters, 7(3): 221-231.
Longo, G. O. and Floeter, S. R. 2012. Comparison of remote video and diver's direct observations to quantify reef
fishes feeding on benthos in coral and rocky reefs. Journal of Fish Biology, 5: 1773-1780.
Page 78 of 115
The Offshore Marine Environment of Ascension Island, South Atlantic
Lubbock, R. 1980. The shore fishes of Ascension Island. Journal of Fish Biology, 17(3): 283-303.
Luiz, O.J. and Edwards, A.J. 2011. Extinction of a shark population within the archipelago of Saint Paul’s Rocks
(equatorial Atlantic) inferred from the historical record. Biological Conservation, 144: 2873-2881.
Luiz, O.J., Madin, J.S., Robertson, D.R., Rocha, L.A., Wirtz, P. and Floeter, S.R. 2012. Ecological traits influencing
range expansion across large oceanic dispersal barriers: insights from tropical Atlantic reef fishes.
Proceedings of the Royal Society B: Biological Sciences, 279(1730): 1033-1040.
Moura, R.L. and Castro-Ricardo, M.C. 2002. Revision of Atlantic sharpnose pufferfish (Tetradontiformes
Tetraodonitdae Canthigaster) with description of new species. Proceedings of the Biological Society of
Washington, 115(1): 32-50.
Muss, A., Robertson, D.R., Stepien, C.A., Wirtz, P. and Bowen, B.W. 2001. Phylogeography of Ophioblennius: the
role of ocean currents and geography in reef fish evolution. Evolution, 55(3): 561-572.
Pinheiro, H.T., Gasparini, J.L. and Joyeux, J-C. 2010. Reef fish mass mortality event in an isolated island off Brazil,
with notes on recent similar events at Ascension, St Helena and Maldives. Marine Biodiversity Records, 3:
e47.
(http://www.journals.cambridge.org/abstract_S1755267210000424)
Pinheiro, H. T., Ferreira, C. E. L., Joyeux, J.-C., Santos, R. G. and Horta, P. A. 2011. Reef fish structure and
distribution in a south-western Atlantic Ocean tropical island. Journal of Fish Biology, 79(7): 1984-2006.
Quero, J.C., Hureau, J.C., Karrer, C., Post A. and Saldanha, L. (eds.). 1990. Check-list of the fishes of the eastern
tropical Atlantic (CLOFETA). JNICT, Lisbon; SEI, Paris; and UNESCO, Paris. Vol. 2.
Renshaw, O. 2011 Ascension Island's Fish Kills 2011. Ascension Conservation Quarterly, 34: 10-11.
Rocha, L.A., Robertson, D.R., Rocha, C.R., Tassell, J.L., Craig, M.T. and Bowen, B.W. 2005. Recent invasion of
the tropical Atlantic by an Indo-Pacific coral reef fish. Molecular Ecology, 14(13): 3921—3928.
Smith, J.L.B. 1965. Acanthurus bahianus Castellnau 1855, in the south-east Atlantic Ocean. Copeia, 1: 110-111.
Vaske, T.J., de Lima, K.L., Ribeiro, A.C.B. and Lessa, R.P. 2008. Record of the St Helena deep water scorpionfish,
Pontinus nigropunctatus (Günther) (Scorpaeniformes: Scorpaenidae) in the Saint Peter and Saint Paul
Archipelago, Brazil. Pan-American Journal of Aquatic Sciences, 3: 46-48.
Wirtz, P., Bingeman, J., Bingeman, J., Fricke, R., Hook, T.J. and Young, J. 2014. The fishes of Ascension Island,
central Atlantic Ocean - new records and an annotated check-list. Journal of the Marine Biological
Association of the United Kingdom, 1-16.
http://www.journals.cambridge.org/abstract_S0025315414001301
Fisheries
Alvarado Bremer, J.R. and Mejuto, J. and Gómez-Márquez, J. and Boán, F. and Carpintero, P. and Rodríguez,
J.M. and Viñas, J. and Greig, T.W. and Ely, B. 2005. Hierarchical analyses of genetic variation of samples
from breeding and feeding grounds confirm the genetic partitioning of northwest Atlantic and South Atlantic
populations of swordfish Xiphias gladius (L). Journal of Experimental Marine Biology and Ecology, 327(2):
167-182.
Álvarez de Quevedo, I., San Félix, M. and Cardona, L. 2014. Temporal trends in the by-catch of loggerhead turtles
Caretta caretta in the Mediterranean Sea. Marine Ecology Progress Series, 504: 303-304.
Armstrong, M.J. and Reeves, S.A. 2015. A review of fisheries management options for Ascension Island waters. 2:
Inshore Fisheries. Unpublished report to Ascension Island Government and the Foreign and
Commonwealth Office. Cefas contract report C6389. 78 pp.
Appleby, T. (2015). Fisheries law in action: An exploration of legal pathways to a better managed marine
environment. DPhil, University of the West of England.
Ascension Island Government. 2004. History of Young's fishing license application.
Block, B.A. 2005. Electronic tagging and population structure of Atlantic bluefin tuna. Nature, 434: 1121-1126.
BlueSky. 2005. Proposal to provide a fishery surveillance and control service to Ascension Island.
Bugoni, L., Neves, T.S., Leite, N.O., Carvalho, D., Sales, G., Furness, R.W., Stein, C.E., Peppes, F.V., Giffoni, B.B.
and Monteiro, D.S. 2008. Potential bycatch of seabirds and turtles in hook-and-line fisheries of the Itaipava
Fleet, Brazil. Fisheries Research, 90(1-3): 217-224.
Campbell, M.S., Stehfest, K.M., Votier, S.C. and Hall-Spencer, J.M. 2014. Mapping fisheries for marine spatial
planning: Gear-specific vessel monitoring system (VMS), marine conservation and offshore renewable
energy. Marine Policy, 45: 293-300.
Page 79 of 115
The Offshore Marine Environment of Ascension Island, South Atlantic
Capietto, A., Escalle, L., Chavance, P., Dubroca, L., Delgado de Molina, A., Murua, H., Floch, L., Damiano, A.,
Rowat, D. and Merigot, B. 2014. Mortality of marine megafauna induced by fisheries: insights from the
whale shark, the world’s largest fish. Biological Conservation, 174: 147-151.
Choat, J.H. and Robertson, D. R. 2006. An ecological survey of the St Helena and Ascension Island populations of
the jack (Epinephelus adscensionis) with a review of management.
Clark, M.R. 2001. Are deepwater fisheries sustainable? The example of orange roughy. Fisheries Research,
51:123–135.
Clark, M.R. and Koslow, J.A. 2007. Impacts of fisheries on seamounts. pp. 413–41. In: Pitcher TJ, Morato T, Hart
PJB, Clark MR, Haggan N, Santos RS, eds. 2007. Seamounts: Ecology, Fisheries and Conservation, vol.
12. Oxford, UK: Blackwell. 527 pp.
Clark, M.R., Vinnichenko, V.I., Gordon, J.D.M., Beck-Bulat, G.Z., Kukharev, N.N. and Kakora, A.F. 2007. Largescale distant-water trawl fisheries on seamounts. pp 361-399. In: Pitcher TJ, Morato T, Hart PJB, Clark MR,
Haggan N, Santos RS, eds. 2007. Seamounts: Ecology, Fisheries and Conservation, vol. 12. Oxford, UK:
Blackwell. 527 pp.
Coelho, R., Fernandez-Carvalho, J. and Santos, M.N. 2013. A review of fisheries within the ICCAT convention area
that interact with sea turtles. Collective Volume of Scientific Papers ICCAT, 69(4): 1788-1827.
Cullis-Suzuki, S and Pauly, D. 2010. Failing the high seas: a global evaluation of regional fisheries management
organizations. Marine Policy, 34(5): 1036-1042.
Danckwerts, D.K., McQuaid, C.D., Jaeger, A., McGregor, G.K., Dwight, R., Le Corre, M. and Jaquemet, S. 2014.
Biomass consumption by breeding seabirds in the western Indian Ocean: indirect interactions with fisheries
and implications for management. ICES Journal of Marine Science.
http://icesjms.oxfordjournals.org/cgi/doi/10.1093/icesjms/fsu093.
Davies, R.W.D., Cripps, S.J., Nickson, A. and Porter, G. 2009. Defining and estimating global marine fisheries
bycatch. Marine Policy, 33(4): 661-672.
Davies, T.K., Martin, S., Mees, C., Chassot, E. and Kaplan, D.M. 2012. A review of the conservation benefits of
marine protected areas for pelagic species associated with fisheries. A report prepared for the International
Seafood Sustainability Foundation. ISSF Technical Report 2012-02.
Dubroca, L., Chassot, E., Floch, L., Demarcq, H., Assan, C. and Delgado de Molina, A. 2013. Seamounts and tuna
fisheries: tuna hotspots or fishermen habits? Collective Volume of Scientific Papers, ICCAT, 69(5): 20872102.
Emson. 2005. Report on Taiwanese Fishing vessel suspected of illegally fishing in Ascension Waters. E-mail
correspondence (possibly same as below?).
Emson. 2006. Reference to illegal fishing in Ascension waters. E-mail correspondence.
Enviro-Fish, Africa. 2005. Fisheries Research Project Ascension Island.
Game, E.T., Grantham, H.S., Hobday, A.J., Pressey, R.L., Lombard, A.T., Beckley, L.E., Gjerde, K., Bustamante,
R., Possingham, H.P. and Richardson, A.J. 2009. Pelagic protected areas: the missing dimension in ocean
conservation. Trends in Ecology & Evolution, 24(7): 360-369.
Gross, M. 2014. Learning to live with sharks. Current Biology, 24: R341--R344.
http://www.sciencedirect.com/science/article/pii/S0960982214004631
Hecht, T and Malan, P. 2007. The Ascension Island fisheries with recommendations for management. Report to
the Ascension Island Government. Grahamstown, South Africa.
Huang, H-W. 2013. Characteristics of sea turtle incidental catch of Taiwanese longline fisheries in the Atlantic
Ocean. Collective Volume of Scientific Papers ICCAT, 69(5): 2233-2238.
Huang, H-W. 2011. Bycatch of high sea longline fisheries and measures taken by Taiwan. Marine Policy, 5: 712720.
Huang, H-W., Chou, S.-C., Dai, J.-P. and Shiao, C.-H. 2009. Overview of Taiwanese observers program for large
scale tuna longline fisheries in Atlantic Ocean from 2002 to 2006. Collective Volume of Scientific Papers
ICCAT, 64(7): 2508-2517.
Huang, H-W and Yeh, Y-M. 2010. Bycatch and discards by Taiwanese large-scale tuna longline fleets in the Indian
Ocean. Fisheries Research, 3: 261-270.
Huang, H-W and Yeh, Y-M. 2011. Impact of Taiwanese distant water longline fisheries on the Pacific seabirds:
finding hotspots on the high seas. Animal Conservation, 14: 562-574.
ICCAT. 2014. Report for the biennial period 2012-13, Part II (2013) Vol. 2. Madrid, Spain.
Joung, S.J., Liu, K-M., Liao, Y.Y. and Hsu, H.H. 2005. Observed by-catch of Taiwanese tuna longline fishery in the
South Atlantic Ocean. Journal of the Fisheries Society of Taiwan, 32(1): 69-77.
Page 80 of 115
The Offshore Marine Environment of Ascension Island, South Atlantic
Kerstetter, D.W, Orbesen, E.S., Snodgrass, D. and Prince, E.D. 2009. Movements and habitat utilization of two
longbill spearfish Tetrapturus pfluegeri in the eastern tropical South Atlantic Ocean. Bulletin of Marine
Science, 85(2): 173-182.
Lewison, R., Crowder, L., Read, A. and Freeman, S. 2004. Understanding impacts of fisheries bycatch on marine
megafauna. Trends in Ecology & Evolution, 19(11): 598-604.
Lewison, R.L. and Crowder, L.B. 2007. Putting longline bycatch of sea turtles into perspective. Conservation
Biology, 21(1): 79-86.
Lighthouse Consortium. 2005. A Proposal to the Ascension Island Government to Develop a Fisheries
Management System.
Martínez, P., González, E.G., Castilho, R. and Zardoya, R. 2006. Genetic diversity and historical demography of
Atlantic bigeye tuna (Thunnus obesus). Molecular Phylogenetics and Evolution, 39(2): 404-416.
Matsumoto, T., Miyabe, N., Saito, H. Okasaki, M. and Chow, S. 2002. Report of 2000-2001 research cruise by R/V
Shoyo-Maru conducted under the ICCAT’s BETYP. Collective Volume of Scientific Papers ICCAT, 54(1):
68-90.
Matsumoto, T., Saito, H. and Miyabe, N. 2005. Swimming behaviour of adult Bigeye Tuna using pop-up tags in the
central Atlantic Ocean. Collective Volume of Scientific Papers ICCAT, 57(1): 151-170.
MRAG. 2010. Report of Fisheries Patrol around Ascension Island, St Helena and Tristan da Cunha. MRAG/Argos
Froyanes Ltd.
Neves, T.S., Mancini, P.L., Nascimento, L., Migueis, A.M.B. and Bugoni, L. 2007. Overview of seabird bycatch by
Brazilian fisheries in the South Atlantic Ocean. Collective Volume of Scientific Papers ICCAT, 60(6): 20852093.
Pearce, J. 2009. Combating IUU fishing in the waters of Ascension, St Helena and Tristan da Cunha: advice on
options, costs and feasibility. MRAG.
Pearce, J., Mees, C., Peatman, T., Mitchell, R., Moir-Clark, J. and Arthur, R. 2010. An overview of pelagic fisheries
for shared highly migratory species in the waters of Ascension, St Helena and Tristan da Cunha and
opportunities for the development of harmonised fisheries management activities. MRAG report.
Pelembe, T.J. 2006. Spear-fishing on Ascension Report by Sea Fisheries Officer Tara Pelembe. Report to the
Ascension Island Government.
Reeves, S.A. and Laptikovsky, V. 2014. A review of fisheries management options for Ascension Island waters. 1:
offshore fisheries. Unpublished report to Ascension Island Government and the Foreign and Commonwealth
Office. Cefas contract report C6389. Lowestoft, Suffolk. 133 pp.
Robertson, D.R., Choat, J.H., Posada, J.M., Pitt, J. and Ackerman, J.L. 2005. Ocean surgeonfish Acanthurus
bahianus. II. Fishing effects on longevity, size and abundance. Marine Ecology Progress Series, 295: 245256.
Sales, G., Giffoni, B.B. and Barata, P.C.R. 2008. Incidental catch of sea turtles by the Brazilian pelagic longline
fishery. Journal of the Marine Biological Association UK, 88(4): 853-864.
Schwenke, K.L. and Buckel, J.A. 2008. Age, growth, and reproduction of dolphinfish, Coryphaena hippurus, caught
off the coast of North Carolina. Fishery Bulletin, 106(1): 82-92.
Scullion, J. 1990. Review of the Fish Resources, Fisheries and Oceanography within the Exclusive Fishing Zone of
Ascension Island. Report to the Overseas Development Administration (DFID) and the St Helena
Government.
Sippela, T., Paige Eveson, J., Galuardi, B., Lam, C., Hoyle, S., Maunder, M., Kleiber, P., Carvalho, F., Tsontos, V.,
Teo, S.L.H., Aires-da-Silva, A. and Nicol, S. 2014. Using movement data from electronic tags in fisheries
stock assessment: A review of models, technology and experimental design. Fisheries Research, 1-9.
http://dx.doi.org/10.1016/j.fishres.2014.04.006
Swimmer, Y., Empey Campora, C., Mcnaughton, L., Musyl, M. and Parga, M. 2014. Post-release mortality
estimates of loggerhead sea turtles (Caretta caretta) caught in pelagic longline fisheries based on satellite
data and hooking location. Aquatic Conservation: Marine and Freshwater Ecosystems, 24(4): 498-510.
Tasker, M.L., Camphuysen, C.J., Cooper, J., Garthe, S., Montevecchi, W.A. and Blaber, S.J.M. 2000. The impacts
of fishing on marine birds. ICES Journal of Marine Science: Journal du Conseil, 57(3): 531-547.
Teo, S.L.H. & Block, B.A. 2010. Comparative influence of ocean conditions on tuna catch from longlines in Gulf of
Mexico. PLoS ONE, 5. http://dx.plos.org/10.1371/ journal.pone.0010756.
Trebilco, R., Halpern, B.S., Flemming, J.M., Field, C., Blanchard, W. and Worm, B. 2011. Mapping species
richness and human impact drivers to inform global pelagic conservation prioritisation. Biological
Conservation, 144(5): 1758-1766.
http://linkinghub.elsevier.com/retrieve/pii/S0006320711000942
Page 81 of 115
The Offshore Marine Environment of Ascension Island, South Atlantic
Tuck, G.N., Phillips, R.A., Small, C., Thomson, R.B., Klaer, N.L., Taylor, F., Wanless, R.M. and Arrizabalaga, H.
2011. An assessment of seabird-fishery interactions in the Atlantic Ocean. ICES Journal of Marine Science,
(8): 1628-1637.
http://icesjms.oxfordjournals.org/cgi/doi/10.1093/icesjms/fsr118
Uhlmann, S., Fletcher, D. and Moller, H. 2005. Estimating incidental takes of shearwaters in driftnet fisheries:
lessons for the conservation of seabirds. Biological Conservation, 123(2): 151-163.
Ward, P. and Myers, R.A. 2005. Shifts in open-ocean fish communities coinciding with the commencement of
commercial fishing. Ecology, 86(4): 835-847.
Weng, K.C., Stokesbury, M.J.W., Boustany, A.M., Seitz, A.C., Teo, S.L.H., Miller, S.K. and Block, B.A. 2009.
Habitat and behaviour of yellowfin tuna Thunnus albacares in the Gulf of Mexico determined using pop up
satellite tags. Journal of Fish Biology, 74(7): 1434-1449.
Yeh, Y-M., Huang, H-W., Dietrich, K. S. and Melvin, E. 2013. Estimates of seabird incidental catch by pelagic
longline fisheries in the South Atlantic. Animal Conservation, 16(2): 141-152.
Yokawa, K. and Saito, H. 2004. Results of comparison of catch ratio between shallow and deep setting obtained
from 2002 Shoyo-maru survey in the tropical Atlantic. Collective Volume of Scientific Papers ICCAT, 56(1):
195-200.
Zagaglia, C.R., Lorenzzetti, J.A. and Stech, J.L. 2004. Remote sensing data and longline catches of yellowfin tuna
(Thunnus albacares) in the equatorial Atlantic. Remote Sensing of Environment, 93(1-2): 267-281.
Zydelis, R., Lewison, R.L., Shaffer, S.A., Moore, J.E., Boustany, A.M., Roberts, J.J., Sims, M., Dunn, D.C., Best,
B.D., Tremblay, Y., Kappes, M.A., Halpin, P.N., Costa, D.P. and Crowder, L.B. 2011. Dynamic habitat
models: using telemetry data to project fisheries bycatch. Proceedings of the Royal Society B: Biological
Sciences, 278(1722): 3191-3200.
Marine Protected Areas
Anderson, A.B., Bonaldo, R.M., Barneche, D.R., Hackradt, C.W., Félix-Hackradt, F.C., García-Charton, J.A. and
Floeter, S.R. 2014. Recovery of grouper assemblages indicates effectiveness of a marine protected area in
Southern Brazil. Marine Ecology Progress Series, 514: 207-215.
Costello, M.J. 2014. Long live Marine Reserves: a review of experiences and benefits. Biological Conservation,
176: 289-296.
Davies, T.K., Martin, S., Mees, C., Chassot, E. and Kaplan, D.M. 2012. A review of the conservation benefits of
marine protected areas for pelagic species associated with fisheries. A report prepared for the International
Seafood Sustainability Foundation. ISSF Technical Report 2012-02.
Devillers, R., Pressey, R.L., Grech, A., Kittinger, J.N., Edgar, G.J., Ward, T. and Watson, R. 2014. Reinventing
residual reserves in the sea: are we favouring ease of establishment over need for protection? Aquatic
Conservation: Marine and Freshwater Ecosystems.
http://doi.wiley.com/10.1002/aqc.2445
Dickey, R. 2014. Letter regarding the creation of a large-scale MPA in Ascension Island's EEZ. AOS (Ascension
Ornithological Society?).
Edgar, G.J., Stuart-Smith, R.D., Willis, T.J., Kininmonth, S., Baker, S.C., Banks, S,. Barrett, N.S., Becerro, M.A.,
Bernard, A.T.F., Berkhout, J., Buxton, C.D., Campbell, S.J., Cooper, A.T., Davey, M., Edgar, S.C.,
Försterra, G., Galván, D.E., Irigoyen, A.J., Kushner, D.J., Moura, R., Parnell, P.E., Shears, N.T., Soler, G.,
Strain, E.M.A. and Thomson, R.J. 2014. Global conservation outcomes depend on marine protected areas
with five key features. Nature, 506: 216-220.
Goldsmith, Z. 2014 (May). Transcript extract from House of Commons debate on sustainability in the Overseas
Territories.
Grüss, A., Kaplan, D.M., Guénette, S., Roberts, C.M. and Botsford, L.W. 2011. Consequences of adult and juvenile
movement for marine protected areas. Biological Conservation, 144(2): 692-702.
Knip, D.M., Heupel, M.R. and Simpfendorfer, C.A. 2012. Evaluating marine protected areas for the conservation of
tropical coastal sharks. Biological Conservation, 148(1): 200-209.
Lascelles, B.G., Langham, G.M., Ronconi, R.A. and Reid, J.B.. 2012. From hotspots to site protection: identifying
Marine Protected Areas for seabirds around the globe. Biological Conservation, 156: 5-14.
Pew Charitable Trusts, Ending Illegal Fishing project: http://www.pewenvironment.org/campaigns/ending-illegalfishing-project/id/8589941944
Proteez. 2004. An EEZ MCS for Ascension Island.
Page 82 of 115
The Offshore Marine Environment of Ascension Island, South Atlantic
Roberts, C., Laffoley, D., Norse, E.A., Meeuwig, J., Pauly, D., Sheppard, C., Rogers, A. and Edgar, G. 2014. The
opportunity for a large scale fully protected marine protected area around Ascension Island.
Rogers, A.D. (Ed.). 2013. The Global State of the Ocean; Interactions Between Stresses, Impacts and Some
Potential Solutions. Synthesis papers from the International Programme on the State of the Ocean 2011
and 2012 Workshops. Marine Pollution Bulletin, 74(2): 491–552.
http://www.stateoftheocean.org/pdfs/IPSO-Papers-Combined-15.1.14.pdf
Ronconi, R.A., Lascelles, B.G., Langham, G.M., Reid, J.B. and Oro, D. 2012. The role of seabirds in Marine
Protected Area identification, delineation, and monitoring. Introduction and synthesis. Biological
Conservation, 156: 1-4.
RSPB. 2014. An Ascension Island Ocean Sanctuary: An Initial Review of Options for Surveillance and
Enforcement. A report for the Centre for Environment, Fisheries & Aquaculture Science, the Ascension
Island Government, & the UK Foreign and Commonwealth Office. RSPB, Sandy, UK.
Sciberras, M., Jenkins, S.R., Mant, R., Kaiser, M.J., Hawkins, S.J. and Pullin, A.S. 2015. Evaluating the relative
conservation value of fully and partially protected marine areas. Fish and Fisheries, 16(1): 58-77.
Singleton, R.L. and Roberts, C.M. 2014. The contribution of very large marine protected areas to marine
conservation: giant leaps or smoke and mirrors? Marine Pollution Bulletin, 87: 7-10.
Yorio, P. 2009. Marine protected areas, spatial scales, and governance: implications for the conservation of
breeding seabirds. Conservation Letters, 2(4): 171-178.
Other
Ainley, D.G. and Spear, L.B. 1990. The incidence of plastic in the diets of pelagic seabirds in the Equatorial Pacific.
In: Shomura, R.S. and Godfrey, M.L. (eds.) Proceedings of the Second International Conference on Marine
Debris, 2-7 April 1989, Honolulu, Hawaii, 653-664.
Angel, M.V. 1993. Biodiversity of the pelagic ocean. Conservation Biology, 7: 760-772.
Ashmole, N.P. and Ashmole, M.J. 1997. The land fauna of Ascension Island: new data from caves and lava flows,
and a reconstruction of the prehistoric ecosystem. Journal of Biogeography, 24(5): 549-589.
Barnes, D.K.A. and Milner, P. 2005. Drifting plastic and its consequences for sessile organism dispersal in the
Atlantic Ocean. Marine Biology, 146(4): 815-825.
Brickle, P., Brown, J., Brewin, P., Dimmlich, W., Arkhipkin, A., Laptikovsky, V., Kupper, F., Tsiamis, K., Van West,
P., Morley, S.A., Browning, S. and Browning, S. 2013. Assessing Ascension Island's shallow marine
biodiversity. Darwin Initiative Overseas Territories Challenge Fund final report.
Ceridwen, I.F., Nikula, R. and Waters, J.M. 2011. Oceanic rafting by a coastal community. The Royal Society
Proceedings B, 278(1706): 649-655.
Clark, M.R., Rowden, A.A., Schlacher, T., Williams, A., Consalvey, M., Stocks, K.I., Rogers, A.D., O’Hara, T.D.,
White, M., Shank, T.M. and Hall-Spencer, J.M. 2010. The ecology of seamounts: structure, function, and
human impacts. Annual Review of Marine Science, 2: 253-278.
Cleverly, R. and Parson, L. 2011. Does Ascension Island have an outer continental shelf?
www.iho.int/mtg_docs/com_wg/ABLOS/ABLOS_Conf6/S9P3-P.pdf
Cothran, D. 2011. First ever look at the Grattan Seamount. Video (mp4) footage shot using an ROV from the
National Geographic Explorer.
Cuninghame, J. 1699. A catalogue of shells, etc. gathered at the island of Ascension, by Mr. James Cuninghame
(Chirurgeon), with what plants he there observed; communicated to Mr. James Petiver (Apothccary), and
Fellow of the Royal Society. Philosophical Transactions, 21: 295—300.
De Forges, B.R., Koslow, J.A. and Poore, G.C.B. 2000. Diversity and endemism of the seamount fauna in the
south-west Pacific. Nature, 405: 944-947.
De Grave, S., Anker, A., Dworschak, P.C., Clark, P.F. and Wirtz, P. 2014. An updated checklist of the marine
Decapoda of Ascension Island, central Atlantic Ocean. Journal of the Marine Biological Association of the
United Kingdom, 1-12.
http://www.journals.cambridge.org/abstract_S0025315414001295
Derraik, J.G.B. 2002. The pollution of the marine environment by plastic debris - a review. Marine Pollution Bulletin,
44: 842-852.
Eriksen, M. 2010. Reflections on the Rio-Ascension voyage. Pangaea Explorations.
Evangelidis, C.P., Minshull, T.A. and Henstock, T.J. 2004. Three-dimensional crustal structure of Ascension Island
from active source seismic tomography. Geophysical Journal International, 159 (1): 311-325.
Page 83 of 115
The Offshore Marine Environment of Ascension Island, South Atlantic
Faneros, G. & Arnold, F. 2003. Geomorphology of two seamounts offshore Ascension Island, South Atlantic
Ocean. Proceedings of Oceans 2003, 22-26 Sept. 2003. Vol. 1, 39-49. Publisher: IEEE.
Gondim, A. I., Dias, T. L. P. and Christoffersen, M. L. 2013. Diadema ascensionis is not restricted to oceanic
islands: evidence from morphological data. Brazilian Journal of Biology, 2: 431-435.
Gunther A., Smith, E.A., Miers, E.J., Waterhouse, C.O., Bell, F.J. and Ridley, S.O. 1881. Report on a Collection
made by Mr. T. Conry on Ascension Island. The annals and magazine of Natural History, vol. 8: 430-440.
Hall, J. 2014. Ascension Island Marine Management Review - RSPB Submission.
Hall-Spencer, J.M., Rogers, A., Davies, J., Foggo, A. 2007. Historical deep-sea coral distribution on seamount,
oceanic island and continental shelf-slope habitats in the NE Atlantic. In Conservation and Adaptive
Management of Seamount and Deep-Sea Coral Ecosystems, ed. R.Y. George, S.D. Cairns, pp. 324. Miami:
Rosenstiel School of Marine and Atmospheric Science.
Hartmannschroder, G. 1992. The Polychaetes of the Amsterdam Expedition to Ascension Island. Bijdragen tot de
dierkunde, 61(4): 219-235.
Hoyle, W.E. 1886. Report on the Cephalopoda Collected by H.M.S. "Challenger" during the Years 1873-76.
Volume 16 in Zoology in Report on the Scientific Results of the Voyage of H.M.S. "Challenger." vi + 246
pages.
Irving, R.A. 1989. A preliminary investigation of the sublittoral habitats and communities of Ascension Island, South
Atlantic. Progress in Underwater Science, 13: 67-78.
John, D.M., Prud'homme van Reine, W.F., Lawson, G.W., Kostermans, T.B. and Price, J.H. 2004. A taxonomic and
geographical catalogue of the seaweeds of the western coast of Africa and adjacent islands. Beihefte zur
Nova Hedwigia 127: 1-339.
http://www.davidjohn02.com/WestAfricanSeaweeds2004.pdf
Johnston, D.W. 1973. Polychlorinated biphenyls in sea birds from Ascension Island, South Atlantic Ocean. Bulletin
of environmental contamination and toxicology, 10(6): 368-371.
Keenlyside, N.S. and Latif, M. 2007. Understanding Equatorial Atlantic interannual variability. Journal of Climate, 7:
131-142.
Klingelhöfer, F., Minshull, T.A., Blackman, D.K., Harben, P. and Childers, V. 2001. Crustal structure of Ascension
Island from wide-angle seismic data: implications for the formation of near-ridge volcanic islands. Earth and
Planetary Science Letters, 190: 41-56.
Koslow JA. 1997. Seamounts and the ecology of deep-sea fisheries. American Scientist, 85:168–176.
Lessios, H.A., Kessing, B.D., Robertson, D. R. and Paulay, G. 1999. Phylogeography of the pantropical sea urchin
Eucidaris in relation to land barriers and ocean currents. Evolution, 53: 806-817.
Lessios, H.A., Kessing, B.D. and Pearse, J.S. 2001. Population structure and speciation in tropical seas global
phylogeography of the sea urchin Diadema. Evolution, 55(5): 955-975.
Levin, L.A. and Gooday, A. 2003. The deep Atlantic Ocean. Ecosystems of the deep oceans (Tyler, P.A. ed.). 111178. Amsterdam: New York: Elsevier.
Longo, G.O., Ferreira, C.E.L. and Floeter, S.R. 2014. Herbivory drives large-scale spatial variation in reef fish
trophic interactions. Ecology and Evolution, 4(23): 4553-4566.
Lumpkin, R. and Garzoli, S.L. 2005. Near-surface circulation in the tropical Atlantic Ocean. Deep Sea Research, I
(52): 495-518.
Maddocks, R.F. 1975. Recent Bairdiidae (Ostracoda) from Ascension Island. Crustaceana, 28: 53-65.
Martins, A.M.A. and Alves Jr, T.J., Furtado Neto, M.A.A. and Lien, J. 2004. The most northern record of Gervais'
Beaked Whale Mesoplodon europaeus (Gervais, 1855), for the Southern Hemisphere. Latin American
Journal of Aquatic Mammals, 2: 151-155.
Melo, P.A.M.C., Júnior, M. de M.,De Macêdo, S.J., Araujo, M. and Neumann-Leitão, S. 2014. Copepod distribution
and production in a Mid-Atlantic Ridge archipelago. Annals of the Brazilian Academy of Sciences, 86(4):
1719-1733.
Morley, S.A., Bates, A.E., Lamare, M., Richard, J., Nguyen, K.D., Brown, J. and Peck, L.S. 2014. Rates of warming
and the global sensitivity of shallow water marine invertebrates to elevated temperature. Journal of the
Marine Biological Association of the United Kingdom, FirstView, 1-7.
www.journals.cambridge.org/abstract_S0025315414000307
Muss, A., Robertson, D.R., Stepien, C.A., Wirtz, P. and Bowen, B.W. 2001. Phylogeography of Ophioblennius: the
role of ocean currents and geography in reef fish evolution. Evolution, 55(3): 561-572.
O’Hara, T.D. 2007. Seamounts: Centres of endemism or species richness for ophiuroids? Global Ecology and
Biogeography, 16: 720–732.
Page 84 of 115
The Offshore Marine Environment of Ascension Island, South Atlantic
Padula, V., Wirtz, P. and Schrödl, M. 2014. Heterobranch sea slugs (Mollusca: Gastropoda) from Ascension Island,
South Atlantic Ocean. Journal of the Marine Biological Association of the United Kingdom, 1-10. available
on CJO2014. doi:10.1017/S0025315414000575.
Pawson, D.L. 1978. The echinoderm fauna of Ascension Island. Smithsonian Contributions to the Marine Sciences,
2: 1-31.
Pelembe, T.J. 2005. Commercial Fishing Ascension Background Brief.
Perrin, W.F. 1985. The former dolphin fishery at St Helena. Report of the International Whaling Commission, 35:
423-428.
Petit, J. and Prudent, G. 2010. Climate Change and Biodiversity in European Union Overseas Entities. IUCN
report. 192 pp.
Piontkovski, S., Williams, R., Ignatyev, S., Boltachev, A. and Chesalin, M. 2003. Structural-functional relationships
in the pelagic community of the eastern tropical Atlantic Ocean. Journal of Plankton Research, 25(9): 10211034.
Price, J.H. & John, D.M. 1977 Subtidal Ecology in Anitgua and Ascension A Comparison. Proceedings of the 11th
Symposium of the Underwater Association at the British Museum, 111-133.
Price, J.H. and John, D.M. 1980. Ascension Island A survey of inshore benthic macroorganisms, communities and
interactions. Aquatic Botany, 9: 251-278.
Rocha, L.A., Bass, A.L., Robertson, D.R. and Bowen, B.W. 2002. Adult habitat preferences, larval dispersal, and
the comparative phylogeography of three Atlantic surgeonfishes (Teleostei: Acanthuridae). Molecular
Ecology, 11(2): 243-251.
Rosewater, J. 1975. An annotated list of the marine mollusks of Ascension Island, South Atlantic Ocean.
Smithsonian Institution Press.
Rudorff, C.A.G., Lorenzzetti, J.A., Gherardi, D.F.M. and Lins-Oliveira, J.E. 2009. Application of remote sensing to
the study of the pelagic spiny lobster larval transport in the tropical Atlantic. Brazilian Journal of
Oceanography, 57: 7-16.
Samadi, S., Bottan, L., Macpherson, E., Richer de Forges, B., Boisselier, M-C. 2006. Seamount endemism
questioned by the geographical distribution and population genetic structure of marine invertebrates. Marine
Biology, 149:1463–1475.
Smith, E.A. 1890. On the marine mollusca of Ascension Island. Proceedings of the Zoological Society of London,
April 1, 1890: 317-322.
Stock, J.H. 1996. Origin of the non-marine aquatic crustacean fauna of St. Helene and Ascension. Proceedings of
the 2nd Symposium of Fauna and Flora of the Atlantic Islands, 5: 455-462.
Trunov, I.A. 2006. Ichthyofauna of seamounts around the island of Ascension and St Helena Island. Journal of
Ichthyology, 46(7): 493-499.
Tsiamis, K., Peters, A.F., Shewring, D.M., Asensi, A.O., Van West, P. and Küpper, F.C. 2014. Marine benthic algal
flora of Ascension Island, South Atlantic. Journal of the Marine Biological Association of the United
Kingdom, 1-8.
http://www.journals.cambridge.org/abstract_S0025315414000952
van Andel, T.H., Rea, D.K., von Herzen, R.P and Hoskins, H. 1973. Ascension Fracture Zone, Ascension Island
and the Mid-Atlantic Ridge. Geological Society of America Bulletin, 84(5): 1527-1546.
Watson, R.B. 1879. Mollusca of H.M.S. Challenger Expedition. Journal of the Linnean Society, Zoology, 14: 692—
695.
Page 85 of 115
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Appendix
Ascension Island ‘Game Fishes’ (as included within the on-line database ‘Fishbase’)
Tylosurus crocodilus hound needlefish
Authority: (Péron & Lesueur, Order: Beloniformes
1851)
Family: Belonidae
Depth range: 0 – 13 m
Max. weight: 6.4 kg
Max. length: 150 cm
No map available
Description: Reef-associated. A pelagic species found on seaward reefs.
Solitary or in small groups. Feeds on fishes. Feared by fishers because they
can cause puncture wounds with their sharp snouts when jumping out of the
water, e.g. when alarmed or attracted to lights at night.
Notes pertinent to Ascension: Tylosaurus sp. recorded by Wirtz et al. (2014), Map: Fishbase
Picture: J-C Baur
but as yet it is currently unknown whether it is the western Atlantic T. acus or
the eastern Atlantic T. rafale which is present at Ascension. Wirtz et al. (2014) Distribution: Western Atlantic: New Jersey, USA to Brazil. Eastern Atlantic: Fernando
Poo, Cameroon, Liberia, and Ascension Island; from Senegal and Guinea; and Cape
do not list T. crocodilus.
Verde.
Reference(s): Fishbase 02Feb14 (‘game fishes’); Wirtz et al., 2014.
IUCN Red List status: Not Evaluated
Caranx crysos blue runner
Authority: (Mitchill, 1815)
Order: Perciformes
Family: Carangidae
Depth range: 0 – 100 m
Max. length: 70 cm
Max. weight: 5.1 kg
Description: Reef-associated. A schooling species generally not far from the
coast. Juveniles often found in association with floating Sargassum. Adults
feed on fishes, shrimps, and other invertebrates. They spawn offshore from
January through August. Eggs are pelagic.
Notes pertinent to Ascension:
Map: Fishbase
Picture: JE Randall
Distribution: Eastern Atlantic: Senegal to Angola, including the western
Mediterranean, St. Paul's Rocks and Ascension Island. Reported from Mauritania.
Western Atlantic: Nova Scotia, Canada to Brazil, including the Gulf of Mexico and the
Caribbean. Also found in Argentina.
Reference(s): Fishbase (‘game fishes’); Wirtz et al., 2014.
IUCN Red List status: Least Concern
86
The Offshore Marine Environment of Ascension Island, South Atlantic
Caranx latus horse-eye jack/yellowjack/big-eye jack
Authority: Agassiz, 1831
Order: Perciformes
Family: Carangidae
Depth range: 0 – 140 m
Max. length: 101 cm
Max. weight: 13 kg
Description: A pelagic schooling species, usually found on offshore reefs.
Feeds on fishes, shrimps and other invertebrates. Eggs are pelagic. The adult
horse-eye jack commonly swims with others in a school, either as one species
or mixed with crevalle jack.
Notes pertinent to Ascension:
Map: Fishbase
Photo: Estrada Anaya
Distribution: Circumtropical (Atlantic, Indian & Pacific Oceans). Commonly found in
the subtropical Atlantic Ocean from Bermuda and the northern Gulf of Mexico and
south to Rio de Janeiro. In the eastern Atlantic, it is found from St. Paul's Rocks to
Ascension Island and, rarely, the in the Gulf of Guinea.
Reference(s): Fishbase (‘game fishes’); Wirtz et al., 2014
IUCN Red List status: Not Evaluated
Caranx lugubris black jack/black trevally
Authority: Poey, 1860
Order: Perciformes
Depth range: 12 – 354 m Max. length: 100 cm
(usually 24 – 65 m)
Family: Carangidae
Max. weight: 18 kg
Description: An oceanic and insular species, very much restricted to clear
oceanic waters. Sometimes seen near drop-off at outer edge of reefs.
Occasionally forming schools. Feed on fishes at night. Eggs are pelagic. The
black jack inhabits deep reefs and reef drop offs, also being common around
oceanic seamounts.
Notes pertinent to Ascension: The species was initially named Caranx Map: Fishbase
Photo: JE Randall
ascensionis by Georges Cuvier in 1833.
Distribution: Circumtropical (Atlantic, Indian & Pacific Oceans). Western Atlantic:
Bermuda and the northern Gulf of Mexico to Brazil. Eastern Atlantic: Azores, Madeira,
St. Paul's Rocks, Ascension Island, Cape Verde, and Gulf of Guinea.
Reference(s): Fishbase (‘game fishes’); Wirtz et al., 2014
IUCN Red List status: Not Evaluated
87
The Offshore Marine Environment of Ascension Island, South Atlantic
Decapterus macarellus mackerel scad
Authority: (Cuvier, 1833)
Order: Perciformes
Family: Carangidae
Depth range: 0 – 400 m
Max. length: 46 cm
Max. weight:
Description: Pelagic-oceanic. Adults prefer clear oceanic waters, frequently
around islands. Sometimes they are found near the surface, but generally
caught between 40 and 200 m depth. Usually seen as fast moving schools
along the reef edges near deep water. They feed mainly on zooplankton.
Eggs are pelagic.
Notes pertinent to Ascension: Photo of species taken by T. Hook at Map: Fishbase
Photo: JE Randall
Ascension (Wirtz et al., 2014).
Distribution: Circumglobal. Western Atlantic: Nova Scotia, Canada and Bermuda to
approximately Rio de Janeiro, Brazil. Appears to be absent from the Gulf of Mexico.
Eastern Atlantic: St. Helena, Ascension, Cape Verde, and Gulf of Guinea; Azores and
Madeira.
Reference(s): Fishbase (‘game fishes’); Wirtz et al., 2014
IUCN Red List status: Not Evaluated
Pseudocaranx dentex white trevally
Authority:
(Bloch
Schneider, 1801)
& Order: Perciformes
Depth range: 10 – 238 m
Max. length: 122 cm
Family: Carangidae
Max. weight: 18.1 kg
Description: Reef-associated. Adults occur in bays and coastal waters.
Schools are found at the surface, in mid-water and on the bottom and are
often associated with reefs and rough bottom. Feed on plankton by ramfiltering and suction feeding and on bottom invertebrates. Eggs are pelagic.
One of the best table fish 'being indeed the salmon of St. Helena'.
Notes pertinent to Ascension:
Map: Fishbase
Photo: A Carvalho Filho
Distribution: Western Atlantic: North Carolina, USA and Bermuda to southern Brazil.
Eastern Atlantic: Mediterranean, Azores, Madeira, the Canary Islands, Cape Verde,
Ascension and St. Helena Island.
Reference(s): Fishbase (‘game fishes’); Wirtz et al., 2014
IUCN Red List status: Not Evaluated
88
The Offshore Marine Environment of Ascension Island, South Atlantic
Trachinotus ovatus pompano
Authority: (Linnaeus, 1758)
Order: Perciformes
Family: Carangidae
Depth range: 50 – 200 m
Max. length: 70 cm
Max. weight: 2.8 kg
Description: Pelagic-neritic. Adults are moderately common in shallow water
in areas of surge. Found in clear waters. Form schools. Small specimens are
regularly caught at night from steep rocky shores. Adults feed on small
crustaceans, molluscs and fishes.
Notes pertinent to Ascension:
Map: Fishbase
Photo: R Freitas
Distribution: Eastern Atlantic: Bay of Biscay, British and Scandinavian waters (rare
vagrant) to Angola, including the Mediterranean Sea and offshore islands.
Reference(s): Fishbase (‘game fishes’); Wirtz et al., 2014
IUCN Red List status: Not Evaluated
Uraspis helvola whitetongue jack
Authority: (Forster, 1801)
Order: Perciformes
Family: Carangidae
Depth range: 50 – 300 m
Max. length: 58 cm
Max. weight:
Description: Reef-associated. Adults are benthopelagic in sandy bottoms at
the foot of the edge of the outer reefs, continental coasts and around islands.
Solitary or forming small schools.
Notes pertinent to Ascension: Photo of this species taken at Ascension by T. Map: Fishbase
Photo: unsw.discoverlife.org
Hook (Wirtz et al., 2014).
Distribution: Circumglobal. Southeast Atlantic: St. Helena and Ascension islands.
Reference(s): Fishbase (‘game fishes’); Wirtz et al., 2014
IUCN Red List status: Not Evaluated
89
The Offshore Marine Environment of Ascension Island, South Atlantic
Promethichthys prometheus roundi escolar
Authority: (Cuvier, 1832)
Order: Perciformes
Family: Gempylidae
Depth range: 80 – 800 m
Max. length: 100 cm
Max. weight: ?
Description: Benthopelagic. Found on continental slopes, around oceanic
islands and submarine rises. Migrate to midwater at night. Feed on fish,
cephalopods and crustaceans. Eggs and larvae are pelagic.
Notes pertinent to Ascension:
Map: Fishbase
Photo: PMN Cambraia Duarte
Distribution: Tropical and warm temperate waters of all oceans. Subtropical; 50°N 36°S, 180°W - 180°E.
Reference(s): Fishbase (‘game fishes’); Wirtz et al., 2014
IUCN Red List status: Not Evaluated
Istiophorus albicans Atlantic sailfish
Authority: (Latreille, 1804)
Order: Perciformes
Family: Istiophoridae
Depth range: 0 – 200 m
Max. length: 315 cm
Max. weight: 58.1 kg
Description: Pelagic-oceanic. Usually found in the upper layers of warm water
above the thermocline, but also capable of descending to rather deep water.
Often migrate into nearshore waters. Occasionally form schools or smaller
groups of 3 to 30 individuals, but often occur in loose aggregations over a
wide area. Feed mainly on small pelagic fishes but also takes bottom-dwelling
organisms.
Notes pertinent to Ascension: Not listed by Wirtz et al. (2014); instead, they Map: Fishbase
Photo: E Baumeier
have listed the Indo-Pacific sailfish Istiophorus platypterus. Some authorities
Distribution: Atlantic Ocean: in tropical and temperate waters approximately 40°N in
believe these two species are one and the same.
the northwest Atlantic, 50°N in the northeast Atlantic, 40°S in the southwest Atlantic,
and 32°S in the southeast Atlantic. Highly migratory species.
Reference(s): Fishbase (‘game fishes’); Wirtz et al., 2014
IUCN Red List status: Not Evaluated
90
The Offshore Marine Environment of Ascension Island, South Atlantic
Katsuwonus pelamis skipjack tuna
Authority: (Linnaeus, 1758)
Order: Perciformes
Family: Scombridae
Depth range: 0 – 260 m
Max. length: 110 cm
Max. weight: 34.5 kg
Description: Pelagic-oceanic. Found in offshore waters; larvae restricted to
waters with surface temperatures of 15°C to 30°C. Exhibit a strong tendency
to school in surface waters with birds, drifting objects, sharks, whales. Feed
on fishes, crustaceans, cephalopods and molluscs; cannibalism is common.
Spawn throughout the year in the tropics. Eggs and larvae are pelagic.
Preyed upon by large pelagic fishes.
Notes pertinent to Ascension: Only recently recorded from Ascension. Photo Map: Fishbase
Photo: R Freitas
of this species taken at Ascension by T. Hook (Wirtz et al., 2014).
Distribution: Cosmopolitan in tropical and warm-temperate waters. Highly migratory
species.
Reference(s): Fishbase (‘game fishes’); Wirtz et al., 2014
IUCN Red List status: Least Concern
Thunnus alalunga albacore (tuna)
Authority:
1788)
(Bonnaterre, Order: Perciformes
Depth range: 0 – 600 m
Max. length: 140 cm
Family: Scombridae
Max. weight: 60.3 kg
Description: Pelagic-oceanic. abundant in surface waters of 15.6° to 19.4°C.
Known to concentrate along thermal discontinuities. Form mixed schools with
skipjack tuna Katsuwonus pelamis, yellowfin tuna Thunnus albacares and
bluefin tuna T. maccoyii. Schools may be associated with floating objects,
including sargassum weeds. Feed on fishes, crustaceans and squids. Eggs
and larvae are pelagic.
Notes pertinent to Ascension: Caught by game fishers at Ascension, though Map: Fishbase
Photo: C Archambault
no photo (Wirtz et al., 2014)
Distribution: Cosmopolitan in tropical and temperate waters of all oceans but not at
the surface between 10°N and 10°S. Often confused with juvenile Thunnus obesus
which also have very long pectorals but with rounded tips. Highly migratory species.
Reference(s): Fishbase (‘game fishes’); Wirtz et al., 2014
IUCN Red List status: Near Threatened
91
The Offshore Marine Environment of Ascension Island, South Atlantic
Thunnus albacares yellowfin tuna
Authority: (Bonaterre, 1788)
Order: Perciformes
Family: Scombridae
Depth range: 1 – 250 m
Max. length: 239 cm
Max. weight: 200 kg
Description: A pelagic-oceanic species occurring above and below the
thermoclines. They school primarily by size, either in monospecific or multispecies groups. Larger fish frequently school with porpoises, also associated
with floating debris and other objects. Feed on fishes, crustaceans and
squids. Eggs and larvae are pelagic.
Notes pertinent to Ascension: Photo of this species taken at Ascension by T. Map: Fishbase
Picture: iotc.org
Hook (Wirtz et al., 2014).
Distribution: Worldwide in tropical and subtropical seas. Highly migratory species.
Reference(s): Fishbase (‘game fishes’); Wirtz et al., 2014
IUCN Red List status: Near Threatened
Thunnus obesus bigeye tuna
Authority: (Lowe, 1839)
Order: Perciformes
Family: Scombridae
Depth range: 0 – 250 m
Max. length: 250 cm
Max. weight: 210 kg
Description: Pelagic-oceanic. Occur in areas where water temperatures range
from 13°-29°C, but the optimum is between 17° and 22°C. Variation in
occurrence is closely related to seasonal and climatic changes in surface
temperature and thermocline. Juveniles and small adults school at the surface
in mono-species groups or mixed with other tunas, may be associated with
floating objects. Adults stay in deeper waters. Eggs and larvae are pelagic.
Feed on a wide variety of fishes, cephalopods and crustaceans during the day
and at night.
Notes pertinent to Ascension: Photo of this species taken at Ascension by T. Map: Fishbase
Photo: culture.teldap.tw
Hook (Wirtz et al., 2014).
Distribution: Atlantic, Indian and Pacific: in tropical and subtropical waters. Highly
migratory species.
Reference(s): Fishbase (‘game fishes’); Wirtz et al., 2014
IUCN Red List status: Vulnerable
92
The Offshore Marine Environment of Ascension Island, South Atlantic
Ascension Island ‘Deep Water Fishes’ (as included within the on-line database ‘Fishbase’)
Ditropichthys storeri
Authority: Goode & Bean, Order:
1895
Cetomimiformes
Family: Cetomimidae
Depth range: 650 – 3400 m
Max. weight: ?
Max. length: 13 cm
Description: Juveniles (less than 3.5 cm) were captured in shallower depth
range (650-877 m). Larger specimens appear to dwell deeper.
Notes pertinent to Ascension:
Map: Fishbase
Drawing: shows typical fish in this
family.
Distribution: Circumglobal. Atlantic Ocean: between 41°N-43°S, in the eastern
Atlantic it is found south of Canary Islands to east of Ascension Island; in the western
Atlantic it is known from the USA to Argentina.
Reference(s): Fishbase (‘deep water fishes’)
IUCN Red List status: Not Evaluated
Euprotomicrus bispinatus pygmy shark
Authority: Quoy & Gaimard, Order: Squaliformes
1824
Family:
Dalatiidae
(?Squalidae)
Depth range: 0 – 1800 m
Max. weight: ?
Max. length: 31 cm
Description: Epi-, meso-, and perhaps bathypelagic at 1->400 m. Occurs at or
near the surface at night, descending to below 400 m (possibly as deep as
1,800 m) during the day. Feeds on squid, bony fishes, and crustaceans.
Ovoviviparous, with 8 young per litter, size at birth between 6 and 10 cm.
Caught with dip-nets and buckets at night
Notes pertinent to Ascension:
Map: Fishbase
Drawing: FAO
Distribution: Circumglobal: In subtropical to temperate waters. Southeast Atlantic:
near Ascension Island, east of Fernando de Noronha Island, and west of Cape of
Good Hope, South Africa.
Reference(s): Fishbase (‘deep water fishes’); Wirtz et al., 2014
IUCN Red List status: Least Concern
93
The Offshore Marine Environment of Ascension Island, South Atlantic
Isistius brasiliensis cookie cutter shark
Authority: Quoy & Gaimard, Order: Squaliformes
1824
Family: Dalatiidae
Depth range: 0 – 3700 m
Max. weight: ?
Max. length: 56 cm
Description: Epi- to bathypelagic. Makes diurnal vertical migrations from below
1,000 m in the day to or near the surface at night. Travels long vertical
distances in excess of 2,000 to 3,000 m on a diel cycle. Feeds on free-living
deepwater prey such as large squid, gonostomatids, crustaceans, but is also a
facultative ectoparasite on larger pelagic animals such as wahoo, tuna,
billfishes, and cetaceans. Specialized suctorial lips and a strongly modified
pharynx allow it to attach to the sides of it prey.
Notes pertinent to Ascension: Not listed by Wirtz et al., 2014.
Map: Fishbase
Photo: Wikipedia
Distribution: Circumtropical. Western Atlantic: Bahamas and southern Brazil. Eastern
Atlantic: Cape Verde, Guinea to Sierra Leone, southern Angola and South Africa,
including Ascension Island.
Reference(s): Fishbase (‘deep water fishes’)
IUCN Red List status: Least Concern
Derichthys serpentinus narrow-necked oceanic eel
Authority: Gill, 1884
Order: Anguilliformes
Family: Derichthyidae
Depth range: 0 – 2000 m
Max. length: 40 cm
Max. weight: ?
Description: Meso- to bathypelagic. Feeds on small fishes and crustaceans.
Notes pertinent to Ascension:
Map: Fishbase
Drawing:
Nature
Canadian
Museum
of
Distribution: Circumglobal: In tropical to temperate waters. Eastern Atlantic: one
confirmed record near Ascension Island.
Reference(s): Fishbase (‘deep water fishes’); Wirtz et al., 2014
IUCN Red List status: Not Evaluated
94
The Offshore Marine Environment of Ascension Island, South Atlantic
Diretmoides pauciradiatus Longwing spinyfin
Authority:
Order: Beryciformes
Family: Diretmidae
Depth range: 0 – 600 m
Max. length: 37 cm
Max. weight: ?
Description: Bathypelagic. Juveniles tend to stay near surface while adults
may descend to 1000 m. Adults are plankton-eaters.
Notes pertinent to Ascension: Wirtz et al. (2014) lists this species but not Map: Fishbase
Photo: Ramjohn, D.D.
Diretmus argenteus, which is listed by Fishbase.
Distribution: Eastern Atlantic: Guinea Bissau to Angola. Western Atlantic: eastern
Florida, Gulf of Mexico, the Caribbean and northern Brazil.
Reference(s): Fishbase (‘deep water fishes’); Wirtz et al., 2014
IUCN Red List status: Not Evaluated
Diretmus argenteus silver spinyfin
Authority: Johnson, 1864
Order: Beryciformes
Family: Diretmidae
Depth range: 0 – 2000 m
Max. length: 28 cm
Max. weight:
Description: Bathypelagic. Juveniles are found from near surface to about 250
m to more than 1,000 m. Largest adults may be benthopelagic. Adults are
plankton-eaters.
Notes pertinent to Ascension: Wirtz et al. (2014) does not list this species but Map: Fishbase
Photo: P. Wirtz
lists Diretmoides pauciradiatus, known as the longwing spinyfish.
Distribution: Circumglobal: In tropical to temperate waters. Eastern Atlantic: Iceland
and British Isles to South Africa including Canary Islands and Ascension Island.
Reference(s): Fishbase (‘deep water fishes’); Wirtz et al., 2014
IUCN Red List status: Not Evaluated
95
The Offshore Marine Environment of Ascension Island, South Atlantic
Diplospinus multistriatus striped escolar
Authority: Maul, 1938
Order: Perciformes
Family: Gempylidae
Depth range: 50 – 1000 m
Max. length: 33 cm
Max. weight: ?
Description: Benthopelagic. Oceanic, migrating upward at night to 100 to 200
m (Ref. 6181). Probably forming schools during daytime (Ref. 6181). Feed on
crustaceans and small fish.
Notes pertinent to Ascension: Not listed by Wirtz et al. (2014)
Map: Fishbase
Drawing: FAO
Distribution: Atlantic, Indian and Pacific: in central water masses. Rather rare, but
relatively abundant in the northwest and southeast Atlantic.
Reference(s): Fishbase (‘deep water fishes’); Wirtz et al., 2014
IUCN Red List status: Not Evaluated
Lepidocybium flavobrunneum Escolar
Authority: (Smith, 1843)
Order: Perciformes
Family: Gempylidae
Depth range: 200 – 1100 m
Max. length: 200 cm
Max. weight: 45 kg
Description: Occurs mainly over the continental slope, down to 200 m and
more. Migrates upward at night. Feeds on squid, crustaceans and a wide
variety of fishes. Flesh oily and may have purgative properties. Sometimes
caught by tuna long-liners.
Notes pertinent to Ascension: Not listed by Wirtz et al. (2014).
Map: Fishbase
Photo: Cambraia Duarte, P.M.N.
Distribution: Tropical and temperate seas of the world. Eastern Atlantic: known from
13°N off Guinea to Lobutu, Angola.
Reference(s): Fishbase (‘deep water fishes’); Wirtz et al., 2014
IUCN Red List status: Not Evaluated
96
The Offshore Marine Environment of Ascension Island, South Atlantic
Gempylus serpens snake mackerel
Authority: Cuvier, 1829
Order: Perciformes
Family: Gempylidae
Depth range: 0 – 600 m
Max. length: 100 cm
Max. weight: ?
Description: Pelagic, strictly oceanic and usually solitary. Adults migrate to the
surface at night while larvae and juveniles are found near the surface during
the day. Feed on fishes, cephalopods and crustaceans.
Notes pertinent to Ascension:
Map: Fishbase
Photo: Cambraia Duarte, P.M.N.
Distribution: Worldwide in tropical and subtropical seas. Adults also often caught in
temperate waters.
Reference(s): Fishbase (‘deep water fishes’)
IUCN Red List status: Not Evaluated
Nealotus tripes black snake mackerel
Authority: Johnson, 1865
Order: Perciformes
Family: Gempylidae
Depth range: 914 – 1646 m
Max. length: 25 cm
Max. weight: ?
Description: Oceanic, epipelagic to mesopelagic, migrating to the surface at
night. Feeds on myctophids and other small fishes, squid and crustaceans.
Notes pertinent to Ascension: Not listed by Wirtz et al. (2014).
Map: Fishbase
Photo: JAMARC
Distribution: Atlantic, Indian and Pacific: in tropical and temperate waters.
Reference(s): Fishbase (‘deep water fishes’); Wirtz et al., 2014
IUCN Red List status: Not Evaluated
97
The Offshore Marine Environment of Ascension Island, South Atlantic
Gigantura chuni Gigantura
Authority: Brauer, 1901
Order: Aulopiformes
Family: Giganturidae
Depth range: 500 – 3000 m
Max. length: 15 cm
Max. weight: ?
Description: The common name for this order is the Telescopefishes. This
peculiar-looking fish have eyes which protrude on stalks. They also have a
long, ribbon-like tailfin.
Notes pertinent to Ascension: Not listed by Wirtz et al. (2014).
Map: Fishbase
Image: (from Wikipedia entry)
Distribution: Atlantic, Indian and Pacific: mainly in tropical areas.
Reference(s): Fishbase (‘deep water fishes’); Wirtz et al., 2014
IUCN Red List status: Not Evaluated
Gigantura indica Telescopefish
Authority: Brauer, 1901
Order: Aulopiformes
Family: Giganturidae
Depth range: 500 – 2000 m
Max. length: 20 cm
Max. weight: ?
Description: The species is rare. Inhabits deep water. Famous for its bizarre
shape and unusual eyes.
Notes pertinent to Ascension: Not listed by Wirtz et al. (2014).
Map: Fishbase
Drawing:
Distribution: Circumglobal: In tropical to subtropical waters. Deep sea.
Reference(s): Fishbase (‘deep water fishes’); Wirtz et al., 2014
IUCN Red List status: Not Evaluated
98
The Offshore Marine Environment of Ascension Island, South Atlantic
Lampris guttatus Opah
Authority: (Brünnich, 1788)
Order: Lampriformes
Family: Lampridae
Depth range: 100 – 500 m
Max. length: 200 cm
Max. weight: 270 kg
Description: Oceanic and apparently solitary. Epi- and mesopelagic. Feeds on
midwater fishes and invertebrates, mainly squids (Ref. 6737). Occasionally
taken as a by-catch of tuna fisheries.
Notes pertinent to Ascension: Not listed by Wirtz et al. (2014).
Map: Fishbase
Image: Mincarone, M.M.
Distribution: Worldwide in tropical to temperate waters. Western Atlantic: Grand
Banks and Nova Scotia (Canada) to Florida (USA), Gulf of Mexico and the West
Indies up to Argentina. Eastern Atlantic: Norway and Greenland to Senegal and south
of Angola.
Reference(s): Fishbase (‘deep water fishes’)
IUCN Red List status: Not Evaluated
Notolychnus valdiviae topside lampfish
Authority: (Brauer, 1904)
Order:
Myctophiformes
Family: Myctophidae
Depth range: 25 – 700 m
Max. length: 6 cm
Max. weight: ?
Description: High-oceanic, epipelagic and mesopelagic. Found between 375700 m during the day and between 25-350 m at night. Size stratification with
depth during the day only. Feed on copepods, conchoecid ostracods and
euphausiids.
Notes pertinent to Ascension: Not listed by Wirtz et al. (2014).
Map: Fishbase
Drawing: SFSA
Distribution: Worldwide distribution in tropical, subtropical and temperate waters.
Eastern Atlantic: west of British Isles and Bay of Biscay to South Africa. Western
Atlantic: Canada to Argentina.
Reference(s): Fishbase (‘deep water fishes’); Wirtz et al., 2014
IUCN Red List status: Not Evaluated
99
The Offshore Marine Environment of Ascension Island, South Atlantic
Nemichthys scolopaceus Slender snipe eel
Authority: Richardson, 1848
Order: Anguilliformes
Family: Nemichthyidae
Depth range: 258 – 4337 m
Max. length:
Max. weight: ?
Description: Occur in midwater, usually below 400 m. Feed on crustaceans
while swimming with its mouth open. Mesopelagic and bathypelagic.
Notes pertinent to Ascension: Not listed by Wirtz et al. (2014).
Map: Fishbase
Drawing: from Wikipedia.org
Distribution: Worldwide in tropical and temperate seas. Western Atlantic: Nova
Scotia, Canada and northern Gulf of Mexico to Brazil. Eastern Atlantic: Spain to
South Africa.
Reference(s): Fishbase (‘deep water fishes’);
IUCN Red List status: Not Evaluated
Barbantus elongatus elongate searsid
Authority: Krefft, 1970
Order: Osmeriformes
Family: Platytroctidae
Depth range: 1800 - 2000 m
Max. length: 18 cm
Max. weight: ?
Description: Bathypelagic
Notes pertinent to Ascension:
Map: Fishbase
Drawing: Typical representative of
this family.
Distribution: Eastern Atlantic: slopes of St. Helena, Ascension and Mid- Atlantic ridge.
Reference(s): Fishbase (‘deep water fishes’); Wirtz et al., 2014
IUCN Red List status: Not Evaluated
100
The Offshore Marine Environment of Ascension Island, South Atlantic
Astronesthes caulophorus
Authority:
Regan
Trewavas 1929
& Order: Stomiiformes
Depth range: 100 m - ?
Max. length: 26 cm
Family: Stomiidae
Max. weight: ?
Description: Oceanic-mesopelagic.
Notes pertinent to Ascension: Not listed by Wirtz et al. (2014).
Map: Fishbase
Drawing: SFSA
Distribution: Eastern Atlantic between 23°30'N and 24°S.
Reference(s): Fishbase (‘deep water fishes’)
IUCN Red List status: Not Evaluated
Astronesthes micropogon
Authority: Goodyear & Gibbs Order: Stomiiformes
1970
Family: Stomiidae
Depth range: 120 – 600 m
Max. weight: ?
Max. length: 8 cm
Description: Bathypelagic. Fairly common in deep oceanic waters, usually
living deeper than 500 m during the day. Smaller individuals migrate to the
near-surface or even surface waters at night. Feeds on midwater fishes and
crustaceans.
Notes pertinent to Ascension: Not listed by Wirtz et al. (2014).
Map: Fishbase
Drawing shows representatives of
this family.
Distribution: Eastern Atlantic: Morocco south to Namibia. Western Atlantic: USA to
the Caribbean Sea including the Gulf of Mexico; from French Guiana to Brazil.
Reference(s): Fishbase (‘deep water fishes’)
IUCN Red List status: Not Evaluated
101
The Offshore Marine Environment of Ascension Island, South Atlantic
Astronesthes niger
Authority: Richardson, 1845
Order: Stomiiformes
Family: Stomiidae
Depth range: unknown
Max. length: 16 cm
Max. weight: ?
Description: Bathypelagic. An oceanic and mesopelagic species usually found
deeper than 500 m during the day. Feeds on midwater fishes and
crustaceans. Most common species taken in surface nets at night.
Notes pertinent to Ascension: Not listed by Wirtz et al. (2014).
Map: Fishbase
Drawing:
Nature
Canadian
Museum
of
Distribution: Atlantic Ocean: through most of the Atlantic, from about 43°N to 36°S,
but absent in the west from 5°N to 20°S. Elsewhere, Indian Ocean.
Reference(s): Fishbase (‘deep water fishes’)
IUCN Red List status: Not Evaluated
Chauliodus minimus
Authority: Parin & Novikova, Order: Stomiiformes
1974
Family: Stomiidae
Depth range: Unknown
Max. weight: ?
Max. length: 15 cm
Description: Bathypelagic, collected offshore in the Atlantic.
Notes pertinent to Ascension: Not listed by Wirtz et al. (2014).
Map: Fishbase
Photo: L.G. Fischer
Distribution: Eastern Atlantic: Congo south to Angola. Western Atlantic: Brazil south
to Argentina.
Reference(s): Fishbase (‘deep water fishes’)
IUCN Red List status: Not Evaluated
102
The Offshore Marine Environment of Ascension Island, South Atlantic
Echiostoma barbatum threadfin dragonfish
Authority: Lowe, 1843
Order: Stomiiformes
Family: Stomiidae
Depth range: 30 – 4200 m
Max. length: 37 cm
Max. weight: ?
Description: Meso- to abyssopelagic.
Notes pertinent to Ascension: Wirtz et al. (2014) does not list this species but Map: Fishbase
Drawing: SFSA
does list Eustomias intermedius, known as the intermediate dragonfish.
Distribution: Eastern Atlantic: Portugal to South Africa except the Gulf of Guinea.
Western Atlantic: USA south to Argentina, including the Gulf of Mexico and the
Caribbean Sea.
Reference(s): Fishbase (‘deep water fishes’)
IUCN Red List status: Not Evaluated
Eustomias intermedius
Authority: Clarke, 1998
Order: Stomiiformes
Family: Stomiidae
Depth range: 632 – 640 m
Max. length:
Max. weight: ?
No map available
Description: Pelagic-oceanic. Deep water.
Notes pertinent to Ascension: Not listed by Wirtz et al. (2014).
Map: Fishbase
Distribution: Atlantic Ocean
Reference(s): Fishbase (‘deep water fishes’);
IUCN Red List status: Not Evaluated
103
Drawing: shows typical fish in this
family.
The Offshore Marine Environment of Ascension Island, South Atlantic
Stomias affinis Günther’s boafish
Authority: Günther, 1887
Order: Stomiiformes
Family: Stomiidae
Depth range: 0 – 3182 m
Max. length: 22 cm
Max. weight: ?
Description: Bathypelagic. Some individuals may migrate to the surface at
night. Feed mainly on myctophids.
Notes pertinent to Ascension: Not listed by Wirtz et al. (2014).
Map: Fishbase
Photo: F. Welter-Schultes
Distribution: Circumglobal in tropical and subtropical waters. Eastern Atlantic:
Mauritania south to Angola. Also across the Atlantic between 0 and 20°N, extending
to 35°N and 39°S in the western part (USA to Argentina).
Reference(s): Fishbase (‘deep water fishes’)
IUCN Red List status: Not Evaluated
Symphysanodon berryi Slope bass
Authority: Anderson, 1970
Order:
Perciformes
Family:
Symphysanodontidae
Depth range: 101 – 406 m
Max. length: 13 Max. weight: ?
cm
Description: Bathydemersal – inhabits rocky bottoms.
Notes pertinent to Ascension: Not listed by Wirtz et al. (2014).
Map: Fishbase
Drawing: FAO
Distribution: Western Central Atlantic: from off North Carolina and Bermuda to
northern South America (including West Indies, Gulf of Mexico, and Caribbean Sea);
off Ascension Island; South Atlantic, from localities well north of St. Helena Island and
west of the Island of Pegalu.
Reference(s): Fishbase (‘deep water fishes’)
IUCN Red List status: Not Evaluated
104
The Offshore Marine Environment of Ascension Island, South Atlantic
Aphanopus intermedius Intermediate scabbardfish
Authority: Parin, 1983
Order: Perciformes
Family: Trichiuridae
Depth range: 300 – 1350 m
Max. length: 100 cm
Max. weight: ?
Description: Benthopelagic. “Of no fisheries interest”.
Notes pertinent to Ascension: Not listed by Wirtz et al. (2014).
Map: Fishbase
Drawing: FAO
Distribution: Atlantic Ocean: in moderately warm and tropical waters. In the eastern
Atlantic, it is found off western Sahara, Congo and Angola, from Sierra Leone
submarine rise and Pilberry Seamount.
Reference(s): Fishbase (‘deep water fishes’)
IUCN Red List status: Not Evaluated
Zenion longipinnis
Authority: Kotthaus, 1970
Order: Zeiformes
Family: Zenionidae
Depth range: 200 – 450 m
Max. length: 11 cm
Max. weight: ?
Description: Bathydemersal.
Notes pertinent to Ascension:
Map: Fishbase
Drawing: shows typical fish in this
family.
Distribution: Eastern Atlantic: Mauritania to Angola, Ascension and St. Helena Islands.
Western Atlantic: off northeast Florida, the Bahamas, Gulf of Mexico, Caribbean to
southern Brazil.
Reference(s): Fishbase (‘deep water fishes’); Wirtz et al., 2014
IUCN Red List status: Not Evaluated
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