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ISSUE NO. 40
SEPTEMBER 2003
newsletter
INSIDE THIS ISSUE:
PRESIDENT’S GREETING
FLASHBACK – FLOTILLA OF RESEARCH
VESSELS VISIT COPENHAGEN
SEAMOUNTS – HOTSPOTS
OF MARINE LIFE
KILLER WHALES DIG
DEEP FOR DINNER
EELS IN CRISIS
ALIENS INVADE THE SEA
CAN AQUACULTURE BE MORE
ENVIRONMENTALLY FRIENDLY
THE ECOSYSTEM APPROACH, ICES
AND THE NORTH SEA
DOES FISHING CAUSE GENETIC
EVOLUTION IN FISH STOCKS?
BULLETIN BOARD
ICES CIEM Newsletter September 2003
Orange roughy are one of the stocks that are frequently overfished at
seamounts. Scientists estimate that it could take decades before these local
“…SEAMOUNTS ARE OFTEN CALLED “OCEANIC OASES”
stocks are able to recover. Photo by John D. M. Gordon (www.sams.co.uk)
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Seamounts – hotspots of marine life
By Telmo Morato
What are seamounts?
Seamounts are undersea mountains (usually of volcanic
origin) rising from the seafloor and peaking below sea
level. Underwater mountains of heights above 1000 m are
considered to be seamounts, those between 500–1000 m
as knolls, and those below 500 m as hills. A seamount tall
enough to break the sea surface is called an oceanic
island, e.g., the islands of Hawaii, the Azores and Bermuda
were all underwater seamounts at some point in the past.
Though most people may be unaware of it, underwater
seamounts are fairly common. Estimates vary, but recent
studies suggest that there may be about 30,000
seamounts of heights over 1000 m in the Pacific Ocean,
about 1,000 in the Atlantic Ocean and an indeterminate
number in the Indian Ocean.
Why are seamounts so important?
Seamounts are hotspots of marine life in the vast realms
of the open ocean. As they stand proud of the surrounding seabed they tend to concentrate water currents and
they can have their own localised tides, eddies and
upwellings (where cold, nutrient-rich, deepwater moves
up along the steep sides of the seamount).
Threats – overfishing and why are seamounts so vulnerable?
Due to the strong localised currents and upwellings, the
plankton biomass is often high over seamounts and this
combined with the constant influx of prey organisms,
means that they can attract large numbers of fish. Marine
mammals, sharks, tuna, and cephalopods all congregate
over seamounts to feed on the rich booty and even
seabirds have been shown to be more abundant in the
vicinity of shallow seamounts. Down on the seabed, volcanic rocks provide lots of space for suspension feeders
such as corals that capitalise on all the food that is swept
around them in the strong currents. This is in sharp contrast to the typical deep-sea habitat where depositfeeding animals rely on food that they eat on or in the
sediment. Though the diversity and exceptionally localized distribution of species living in these unique communities are acknowledged, their biology and life history
remain poorly studied, except for indications that some of
these species may be extremely long-lived; some are
thought to live for more than 100 years.
Due to the large stocks of top predators, species diversity
and uniqueness compared to the surrounding ocean,
seamounts are often called “oceanic oases”.
Global fish catches have declined
steadily since the 1980s, and it is now
widely acknowledged that the
world’s fisheries resources are in
serious danger of depletion, undoubtedly due to poor management practices and increased fishing pressure.
Unsustainable fishing practices along
with an excessive level of investment
in fishing capacity have resulted in
serious stock depletion on most continental shelves, thus creating new
pressures on alternative fishing
grounds. In particular, seamounts are
among those “newly” targeted
ecosystems that, since the second half
of the 20th century, have been intensively fished.
Deepwater fisheries in general and
seamounts fisheries in particular,
exhibit a boom and bust sequence,
crashing within about ten years of
their initial development. This was
the case with the orange roughy
(Hoplostethus atlanticus) fisheries off
New Zealand, Australia, and even in
the North Atlantic, the pelagic
armourhead (Pseudopentaceros
wheeleri) fisheries over seamounts in
international waters off Hawaii, and
the blue ling (Molva dipterygia) fisheries in the North Atlantic. As
seamounts are rapidly depleted, the
continued existence of the fisheries
on them depends upon the discovery
of unexploited seamounts with large
fish aggregations.
The species targeted by fisheries at
seamounts have a very low overall
abundance, but they aggregate at
seamounts as part of their life cycle
strategy, e.g., for spawning. They are
often long-lived, slow-growing, late
maturing (at about 30 years), and
have low reproductive potential.
Therefore if they are fished out, it is
thought that it could be decades
before these localised stocks recover;
particularly as they are thought to
Marine mammals, sharks, tuna and cephalopods (e.g., squid) and even seabirds
all congregate over seamounts to feed on the rich booty of marine life.
Photo by Brandon Cole, Nature Picture Library
Map showing the distribution of
seamounts in the Northeast Atlantic
ICES CIEM Newsletter September 2003
“KILLER WHALES WORKING AS A TEAM TO HERD SHOALS
OF 50,000 TO 75,000 HERRING UP TO THE SURFACE”
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Killer whales dig deep for dinner
have limited exchange with other seamounts. This makes
these fish communities very vulnerable to overfishing
and the problem is even more pronounced in seamounts
located in international waters where effective management strategies and agreements are frequently absent.
Depletion of fish stocks is not the only concern. Extensive
trawling activities on seamounts are damaging benthic
(bottom-living) communities, particularly dominant communities of corals and other suspension feeders. The
impact of trawling on complex seamount reefs appears to
be dramatic, with the result of the complete removal of
coral substrate and associated community from the most
heavily fished seamounts. Such massive removal of
natural and structural components of the ecosystem has
negative consequences on seamount biodiversity.
Evidence of such negative impacts has been recorded by
declining fish stocks associated with seamount fishing in
Australia. There are also concerns that damage by deepwater trawling to coldwater coral reefs in the NE Atlantic,
could extend to seamount areas. Unregulated small-scale
fishing can also disturb these sensitive environments,
e.g., the decline in important fish stocks exploited by
small-scale fisheries in the Azores.
Outlook for the future
There is a rising concern about the threats to seamount
ecosystems in the Exclusive Economic Zones of coastal
states and in the high seas and consequently, Canada,
Australia and New Zealand have begun to take the first
steps towards protecting seamounts. In the Atlantic, no
such protective measures have been established but the
OSPAR Commission has placed seamounts on their initial
list of threatened and declining species and habitats that
require conservation action. Mechanisms to provide this
protection will now be considered. The developing OSPAR
Marine Protected Areas programme should provide one
possible mechanism.
In addition, seamounts dominated by hard substrata in
the waters of the European Community may qualify for
site protection under the European Habitats Directive
(1992, Natura 2000 code 1170 “reefs” in the Interpretation
Manual of European Union Habitats EUR 15/2). Portugal
(Azores Region) may nominate one of the seamounts in
their EEZ as a candidate for a Marine Protected Area
(MPA) under the OSPAR convention.
The new OASIS Project
Today, little is known about seamount ecosystems in the
NE Atlantic, or the impact of human activities upon these
unique oceanic ecosystems, mainly due to lack of funding
for research into these systems. A possible sign of change
is that the European Commission has agreed to fund the
first European seamount study integrating physical, biogeochemical and biological research - “the OASIS project”
(OceAnic Seamounts: an Integrated Study).
Until more is known about these fragile ecosystems and
the long-term impacts of fishing and other human activities, the precautionary principle should be applied to
seamounts to ensure their necessary protection and management. In some fisheries, this may require changes in
fishing practice, such as switching from trawling to longlining to minimise disturbance to seabed habitats and
associated fauna. Other fisheries may simply be unsustainable and therefore unacceptable practice on
seamounts.
Author
Telmo Morato
Fisheries Center
University of British Columbia
2204 Main Mall, Vancouver
British Columbia
V6T 1Z4
Canada
E-mail: [email protected]
For more information on the ICES advice on deep sea
fisheries, please consult:
ICES (2001) Answer to Special Request on the Management of Deep-water Species. Cooperative Research Report
No. 246.
www.ices.dk/committe/acfm/comwork/report/2001/oct
/Deep-sea-request.pdf
For description of the OASIS project, please see:
www.biologie.unihamburg.de/ihf/de/projects/index.htm
Other useful websites
WWF North-East Atlantic Programme
www.ngo.grida.no/wwfneap/overview/overfset.htm
EU Habitats Directive
www.europa.eu.int/comm/environment/nature/habdir.
htm
Tasmanian Seamounts Marine Reserve
www.ea.gov.au/coasts/mpa/seamounts/
Killer whales, or Orcas as they are otherwise known, are
fascinating top predators, adapted to live in all major
oceans. Their global distribution and distinct black and
white markings make them one of the most recognizable
of all cetaceans. They are highly social animals with
advanced communication systems and hunting techniques. Examples of their hunting methods include swimming on to beaches at full speed to catch seals in Patagonia, tipping sleeping seals off icebergs in Antarctica,
“turning off” their sonar during hunts to avoid being
heard by seals in British Columbia, and extended group
hunts to separate grey whale calves from their mothers
and then attack them, along the coast of California.
The common theme running through all these behaviours is that they take place on or near the surface where
we can see what is going on. Until recently, killer whale
behaviour below the surface remained largely guesswork
but new advances in acoustic technology now allow us to
‘see’ what they are doing underwater. Here we document
their activities when feeding on Norwegian springspawning herring, and what could be one of the most
advanced hunting behaviours so far observed in the
marine environment.
By Leif Nøttestad, Anders Fernö and Bjørn Erik Axelsen