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Marine Science Training
Handbook
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Table of Contents
CHAPTER 1: THE NATURAL HISTORY OF BELIZE .................................................... 5
1.1:
A brief paleological history .......................................................................................... 5
1.2:.......................................................................................................................................................... 6
Modern Climate ................................................................................................................................. 6
1.3:.......................................................................................................................................................... 6
Conservation Importance of Belize ............................................................................................ 6
1.4:.......................................................................................................................................................... 6
Bacalar Chico Marine Reserve and National Park (BCMRNP) .......................................... 6
CHAPTER 2: BLUE VENTURES CONSERVATION AND THE BELIZE PROJECT .. 8
2.1:.......................................................................................................................................................... 8
Blue Ventures Conservation ......................................................................................................... 8
2.2:
Belize Project .................................................................................................................... 8
2.3:
Sarteneja: An Opportunity to Affect the Entire Coastline of Belize ............... 9
Conservation through Collaboration and Partnership .....................................................10
The Sarteneja Alliance for Conservation and Development (SACD) ......................................... 10
Wildtracks ......................................................................................................................................................... 11
Corozal Sustainable Future Initiative (CSFI) ....................................................................................... 11
The Belize Fisheries Department ............................................................................................................. 11
The Belize Forest Department .................................................................................................................. 11
World Wildlife Fund (WWF) ...................................................................................................................... 11
University of Belize ........................................................................................................................................ 12
Healthy Reefs for Healthy People ............................................................................................................ 12
Southern Environmental Association .................................................................................................... 12
CHAPTER 3: I ...................................................................................................................... 13
NTRODUCTION TO CORAL REEFS ............................................................................... 13
Coral Reefs ........................................................................................................................................13
Structure of Corals Reefs .............................................................................................................13
Where Reefs Exist ...........................................................................................................................13
Ecosystem Interactions ................................................................................................................14
Coral Reefs ......................................................................................................................................................... 14
Seagrass beds ................................................................................................................................................... 14
Mangroves ......................................................................................................................................................... 14
CHAPTER 4: DISTURBANCES TO CORAL REEFS ..................................................... 16
Storms and Cyclones......................................................................................................................16
Coral Bleaching................................................................................................................................16
Nutrient Enrichment .....................................................................................................................17
Overfishing and Destructive Fishing Practices ....................................................................17
Anchor and Diver Damage...........................................................................................................17
CHAPTER 5: FISH BIOLOGY AND IDENTIFICATION .............................................. 18
Class Osteichthyes - Bony Fish ...................................................................................................18
Class Chondrichthyes - Cartilaginous fishes .........................................................................19
Introduction to fish behaviour ..................................................................................................20
Diversity ............................................................................................................................................................. 20
Schooling ............................................................................................................................................................ 20
Territoriality ..................................................................................................................................................... 21
Colouration........................................................................................................................................................ 21
Symbiosis ........................................................................................................................................................... 21
Reproduction, spawning and nesting..................................................................................................... 21
Sequential hermaphroditism ..................................................................................................................... 22
CHAPTER 6: ........................................................................................................................ 22
COMMON FISH FAMILY IDENTIFICATION ................................................................ 22
Identifying fish families ...............................................................................................................22
Scaridae – Parrotfish .....................................................................................................................23
Labridae – Wrasse ..........................................................................................................................23
Pomacentridae – Damselfish ......................................................................................................24
Chaetodontidae – Butterflyfish..................................................................................................24
Pomacanthidae – Angelfish .........................................................................................................25
Acanthuridae – Surgeonfish........................................................................................................26
Serranidae – Groupers, Hamlets and Soapfish.....................................................................26
Balistidae – Triggerfish ................................................................................................................27
Monocanthidae – Filefish .............................................................................................................27
Lutjanidae – Snappers...................................................................................................................28
Haemulidae – Grunts .....................................................................................................................28
Scorpaenidae – Scorpionfish ......................................................................................................28
Carangidae – Jacks ..........................................................................................................................29
Sphyraenidae – Barracuda ..........................................................................................................29
Scombridae – Mackerel ................................................................................................................30
Elopidae - Tarpon ...........................................................................................................................30
Gerreidae - Mojarras .....................................................................................................................31
CHAPTER 7: COMMON MEGAFAUNA IDENTIFICATION ....................................... 31
Elasmobranchs (sharks and rays) ............................................................................................31
Bull Shark (Carcharhinus leucas)
......................................................................................................... 31
Caribbean Reef Shark (Carcharhinus perezi)
.................................................................................. 32
Blacktip Shark (Carcharhinus limbatus)
........................................................................................... 33
Whale Shark (Rhincodon typus)
........................................................................................................... 33
Tiger Shark (Galeocerdo cuvier)
........................................................................................................... 34
Great Hammerhead Shark (Sphyrna mokarran) ............................................................................... 34
Scalloped Hammerhead Shark (Sphyrna lewini)
........................................................................... 35
Caribbean Round Stingray (Himantura schmardae)
.................................................................... 35
Southern Stingray (Dasyatis Americana)
.......................................................................................... 36
Spotted Eagle Ray (Aetobatus narinari)
............................................................................................ 36
Yellow stingray (Urolophus jamaicensis)............................................................................................. 37
Lesser Electric Ray (Narcine bancroftii) ............................................................................................... 37
Turtles ................................................................................................................................................38
Hawksbill Turtle (Eretmochelys imbricata)
.................................................................................... 39
Green Turtle (Chelonia mydas)
............................................................................................................. 40
Loggerhead Turtle (Caretta caretta)
................................................................................................... 40
Leatherback Turtle (Dermochelys coriacea)
................................................................................... 41
Olive Ridley Turtle (Lepidochelys olivacea) ....................................................................................... 41
Mammals ...........................................................................................................................................42
Bottlenose Dolphin (Tursiops truncates)
.......................................................................................... 42
Atlantic Spotted Dolphin (Stenella frontalis)...................................................................................... 42
West Indian Manatee (Trichechus manatus)
................................................................................... 43
CHAPTER X: INTRODUCTION TO PLANTAE AND IDENTIFICATION ................ 44
Turf algae...........................................................................................................................................44
Fleshy Macroalgae ..........................................................................................................................45
Dictyota spp.
.................................................................................................................................................. 45
Lobophora spp. ................................................................................................................................................ 45
Crustose coralline algae (CCA)
............................................................................................................... 46
Articulated coralline algae .......................................................................................................................... 46
4.4. Seagrass...................................................................................................................................................... 46
4.5. Cyanobacteria/Blue green algae...................................................................................................... 47
CHAPTER X: COMMON INVERTEBRATE PHYLA AND IDENTIFICATION......... 48
Phylum Porifera (Sponges) .........................................................................................................48
Phylum Mollusca .............................................................................................................................50
Gastropoda........................................................................................................................................50
Flamingo tongue .............................................................................................................................51
Phylum Echinodermata (Sea Urchins and Sea Cucumbers) ............................................51
Echinoidea (Sea Urchins) .............................................................................................................52
Holothuroidea (Sea Cucumbers)...............................................................................................53
Phylum Chordata (Tunicates) ....................................................................................................53
Solitary tunicate ..............................................................................................................................54
Colonial/encrusting tunicate .....................................................................................................54
Lobsters..............................................................................................................................................55
Caribbean Spiny Lobster (Panulirus argus)
..................................................................................... 55
Spotted spiny lobster (Panulirus guttatus) ......................................................................................... 55
Spanish lobster (Scyllarides aequinoctialis)
.................................................................................... 56
Phylum Cnidaria (Corals, Anemones, Hydroids, and Jellyfish) ......................................56
Scyphozoa (True Jellyfish) .......................................................................................................................... 57
Anthozoa (Gorgonians, Corals, Anemones) ......................................................................................... 58
Hydrozoa (Hydrozoans) .............................................................................................................................. 61
Millepora spp. (Fire Coral)
...................................................................................................................... 61
CHAPTER X: ORDER SCLERACTINIA: INTRODUCTION AND IDENTIFICATION63
Acroporidae ......................................................................................................................................64
6.2. Poritidae ....................................................................................................................................65
6.3. Siderastreidae .........................................................................................................................65
6.6. Faviidae ......................................................................................................................................67
6.7. Meandrinidae...........................................................................................................................68
6.8. Caryophylliidae .......................................................................................................................68
6.9. Mussidae ....................................................................................................................................69
CHAPTER 1: THE NATURAL HISTORY OF BELIZE
Belize lies in the western Caribbean and is bordered to the north by Mexico, to the west and
south by Guatemala and to the east by the Caribbean Sea. It is a small country, only covering
23,000 square kilometres, but for its size boasts a wide biodiversity and cross section of
habitats. The population is also small at only 300,000 people. However, largely due to
immigration, the population is rapidly expanding and with the majority of population centres
being on the coast, fast development is having an impact.
Belize has a diverse range of environmental conditions supporting a number of terrestrial and
marine ecosystems. The region consists of the extensive Maya mountains, swampy lowlands in
the north and coastal plains in the south, with tropical forest, mangroves and coral reefs all in
close proximity. The climate and habitat promote biodiversity with numerous terrestrial species
of flora and fauna and a high diversity of marine species. The coastline is lined with coral reef
and sandy island formations called cayes.
The 320 km long Belize Barrier Reef, forms the heart of the Mesoamerican Barrier Reef System
– the largest barrier reef in the western hemisphere and the second largest in the world. The
diversity and quality of the reef have led to the reef being considered one of the seven wonders
of the underwater world (http://www.7wonders.org/underwater-wonders/).
Coastal lagoons and mangroves cover much of the coastline, providing ideal breeding grounds
and habitat for juvenile species, as well as the home to the charismatic Antillean manatee,
classified as “Endangered” by the IUCN Red List. Combined, these factors make the Belize
coastal region one of great ecological value and importance.
1.1: A brief paleological history
25 million years ago, the Cocos tectonic plate began to move and slide under the Caribbean
plate. This movement resulted in large-scale volcanic activity, with magma chambers erupting
from the sea floor. These slowly grew to form an archipelago of submarine volcanoes, between
Panama and Guatemala, eventually leading to the formation of islands. Sediment and rock from
North and South America slowly deposited between the islands, finally coalescing
approximately 3 million years ago to form a continuous, narrow, landmass between the two:
Central America.
The formation of Central America altered the flow of water between the Pacific and Atlantic
Oceans, forcing Atlantic water north and resulting in the formation of the Gulf Stream. The
development of a land bridge between North and South America played a key role in facilitating
biotic exchange between the two regions, allowing the expansion of animal and plant species’
ranges.
The result has been that Belize has biotic features of both North and South America further
leading to an impressively rich biodiversity.
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1.2: Modern Climate
Located south of the Tropic of Cancer, Belize has a tropical climate, with gentle breezes and
golden sunshine for much of the year, as well as distinct windy, wet and dry seasons.
Temperatures are dependent upon elevation, proximity to the coast and the subsequent effects
of the north-east trade winds from the Caribbean Sea. The annual mean temperature is 26°C
(79°F), with 85% humidity. Sea surface temperatures (24-28°C / 75-84°F) are ideal for coral reef
formation.
Blue Ventures research site is based in the north of Belize. The northern region receives the
lowest annual rainfall, an average of 127 cm per year. The Norte season, characterised by cool,
northerly winds, occurs from November to February, followed by the dry season (March to
June). The wet season occurs during the summer months, from July to October. Belize’s
hurricane season is from June to October, however a ‘direct hit’ has not been experienced since
2000.
A wide range of habitats is found in Belize: tropical forest (60% of Belize remains forested),
lowland savannahs and the Maya mountains inland, lagoons, mangrove, and littoral forest
along the coast, and coral cayes and the majestic barrier reef offshore.
1.3: Conservation Importance of Belize
The Belize Barrier Reef System (BBRRS), a UNESCO World Heritage Site (WHS), forms the core of
the Mesoamerican Barrier Reef System (MBRS). The area was originally nominated because of
its great biodiversity, which provides habitat to a number of species of conservation concern.
However, growing threats from climate change and direct human impacts have resulted in
decreasing general reef health and declines in fish stocks, leaving the system vulnerable to
further deterioration if there is no immediate action to mitigate these threats. The BBRRS-WHS
is now listed as a World Heritage Site in Danger.
1.4: Bacalar Chico Marine Reserve and National Park (BCMRNP)
BCMRNP was established in 1996 as the result of lobbying by local fishermen from the village of
Sarteneja, the largest fishing community in Belize and mainland site for Blue Ventures. It is
hoped that by incorporating these local communities into conservation initiatives, the chance
of long-term success of the reserve can be greatly increased.
Blue Ventures’ Bacalar Chico Dive Camp (BCDC) is located in Bacalar Chico Marine Reserve
(BCMR) on Ambergris Caye. It is home to a number of species of international concern,
including the charismatic Antillean manatee, critically endangered hawksbill turtle (Figure 0-1)
and goliath grouper, Yucatan endemics, such as the increasing threatened black cat bird, and
critically endangered staghorn and elkhorn corals (Acropora palmata, A. cervicornis).
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Figure 0-1 Hawksbill turtle
Much of the wildlife in Bacalar Chico resembles the Yucatan endemics, with 187 bird, 40
mammalian, 55 reptilian and 22 amphibian species. The expansive Cantena Lagoon contains
small mangrove cayes, providing important breeding grounds for marine and coastal birds,
while the mangrove roots provide nursery grounds for reef fish. The sandy beach provides an
important nesting site for loggerhead and green turtles.
Figure 0-2 Map of Bacalar Chico National Park and Marine Reserve.
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BCMR is also a key part of an international system of connected MPAs (Figure 0-2); Arrecife de
Xcalak in Mexico borders the Preservation Zone (northern BCMR), and Corozal Bay Wildlife
Sanctuary borders BCMR at Deer Caye, to the east. In turn, Corozal Bay Wildlife Sanctuary is
connected to Sanctuario Del Manati in Chetumal Bay, Mexico. Imminent plans to extend the
management area of Hol Chan Marine Reserve will further increase connectivity between these
sites.
CHAPTER 2: BLUE VENTURES CONSERVATION AND THE BELIZE
PROJECT
2.1: Blue Ventures Conservation
Blue Ventures’ mission is to encourage the sustainable use of marine resources in order to
conserve tropical coastal habitats, through working with coastal communities in developing
countries to help them build the skills and knowledge they need to protect the marine
environments on which their livelihoods depend.
2.2: Belize Project
In Belize, Blue Ventures operates in two areas, working towards one goal: science-led,
ecosystem-based management, enabling long-term use of Belize’s coastal and marine
resources.
We do this through research and monitoring of MPAs, education and outreach with stakeholder
communities and international volunteers, promotion of sustainable, alternative livelihoods,
often through the development of innovative, market-driven solutions, and collaboration with
national and international bodies.
Sarteneja is the largest fishing community of Belize, with 80% of households directly dependent
upon fishing as their primary source of income. It sits on the shores of Corozal Bay Wildlife
Sanctuary (CBWS), designated for the protection of the endangered Antillean manatee, but also
supporting an active bull shark nursery, bird nesting habitat, extensive mangroves, and an
artisanal fishery. In Sarteneja, collaboration with schools, resource managers and users aim to
increase awareness of environmental threats and participation in the development and
management of target species and habitats. Blue Ventures’ office in Belize is located in
Sarteneja.
Bacalar Chico is one of seven MPAs forming the UNESCO World Heritage Site. There is no
community directly adjacent to the protected area, which is primarily used for tourism from
San Pedro, and a limited amount of fishing from Sartenejan and San Pedrano fishers. Blue
Ventures established its coral reef monitoring programme in Bacalar Chico as it was recognised
to be a relatively data deficient portion of the Belize Barrier Reef. Blue Ventures’ research and
dive camp (BCDC) is in BCMR.
In Belize, through volunteer assistance, Blue Ventures aims to:

Further coastal conservation in BCMR and CBWS, and contribute to wider conservation efforts
in Belize and the Mesoamerican Barrier Reef System (MBRS).
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



Assist coastal communities in improving marine resource management and conservation
efforts.
Provide technical assistance for the effective monitoring and management of MPAs in Belize.
Build capacity for local management of resources, through primary, secondary and tertiary
educational programmes.
Promote integration into sustainable alternative livelihoods and fishery target species, such as
the invasive lionfish.
2.3: Sarteneja: An Opportunity to Affect the Entire Coastline of Belize
The village of Sarteneja, population 3000, is located along the coast of Corozal Bay (Figure 0-1).
This shallow bay in the north of the country hosts a broad diversity of habitats including
estuaries, mangroves and seagrass beds. It is bound by the Mexican mainland to the north,
Belizean mainland to the west and Ambergris Caye, a southerly extension of the Yucatan
peninsula, to the east. In the south, the bay empties into the wide reef flats of Belize, which in
turn drain to the Caribbean Sea. This protected bay affords the fishermen of Sarteneja a
sheltered launching point for their boats, with which they harvest fish, lobster and conch from
the entire length of the Belizean coast.
Figure 0-1 Map showing the location of Sarteneja (Image from Google Earth, February
2010).
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Until the 1950s the small village of Sarteneja was a largely agricultural community, with a
tradition for wooden sailboat building due to an historical use of Sarteneja as a trading post.
However, a direct hit from Category 5 Hurricane Janet in 1955 destroyed houses, crops and
contaminating the soil with salt. In the aftermath the village was rebuilt with the hurricaneresistant concrete structures that remain today, and the villagers turned from their ruined
fields to a new lucrative export market for seafood that had opened for lobster and conch.
Sarteneja’s characteristic wooden sailboats access all portions of the Belize Barrier Reef System,
as far south as the Sapodilla Cayes, near the Guatemalan border. They a familiar sight
throughout the atolls and reefs along the coast, each carrying between 8 and 14 fishermen,
who fish by free diving; gathering conch and lobster by hand, and fish by spear.
For several decades Sarteneja prospered on their newfound industry. However, as the
population and market grew, the inevitable started to happen. The availability of resources
began to decline, whilst the number of fishers continues to increase. Today many fishermen
seek work in other areas, particularly the tourist industry, but jobs are hard to come by, so for
many the only option is to fish longer and harder to try and ensure there is still an income to
support their families.
Historically there has been relatively little NGO involvement in the Sartenejan community,
despite the use they make of the marine resources within Belize. One local NGO established in
1990, Wildtracks, has had a clear impact in Sarteneja and marine resource use throughout
Belize, through their diverse programme responding to terrestrial and marine conservation
issues. Further, the community has started taking steps of its own to provide environmental
education and conservation efforts through the formation of the Sarteneja Alliance for
Conservation and Development (SACD) in the last four years. Blue Ventures is working closely
with this community-led NGO to foster greater care of the immediate environment around the
Corozal Bay and also provide education and conservation advice to the fishing community to
help manage their marine resources.
Conservation through Collaboration and Partnership
Blue Ventures have developed close links with several local organisations involved in
conservation work, throughout Belize, and specifically around Sarteneja and Bacalar Chico.
These partners include the following:
The Sarteneja Alliance for Conservation and Development (SACD)
Established in September 2008, SACD aims to bring people together to promote conservation
and sustainable development. It is the co-manager of Corozal Bay Wildlife Sanctuary, a
responsibility shared with the Belize Forest Department.
The alliance consists of core SACD staff as well as:
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

The Sarteneja Tour Guides Association (STGA), a group aimed at developing the tourism in the
area to alleviate reliance on fishing.
The Sarteneja Fishermen Association (SFA), established to provide Sarteneja’s fishermen with
mechanisms to encourage sustainable alternatives to fishing, reducing their dependence on
fishing.
Wildtracks
Established in 1990, Wildtracks is a multi-faceted non-profit organisation involved in policylevel advisory, protected area assessment and management, education, outreach and capacity
building. Wildtracks also runs Belize’s only manatee and primate rehabilitation centres.
Corozal Sustainable Future Initiative (CSFI)
CSFI manages the Shipstern Nature Reserve, a large terrestrial conservation area adjacent to
Sarteneja, encompassing several inland lagoons, large mangrove areas and extensive tracts of
forest.
The Belize Fisheries Department
This governmental department is the responsible for the management of Belize’s aquatic and
marine resources, and is the primary manager of all Belize’s marine reserves. In some areas, the
Belize Fisheries Department (BFD) has developed partnerships with NGOs to jointly manage the
area. BFD is the sole manager of Bacalar Chico, where Blue Ventures conducts extensive
ecosystem and resource monitoring to provide management advise through regular
communication and in annual reports.
The Belize Forest Department
The Forest Department manages Belize’s terrestrial environments and natural resources
including Bacalar Chico National Park and co-management (with SACD) of Corozal Bay Wildlife
Sanctuary.
World Wildlife Fund (WWF)
An international NGO that performs site-specific conservation throughout the world and has
extensive experience developing conservation programmes in Belize. WWF, with their history
and experience throughout Central America, provide scientific guidance and advice on
operating in Belize and share information and experiences with other conservation efforts in
neighbouring countries.
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University of Belize
This is the principal university within Belize and has a dedicated department for marine
environmental research and tertiary education.
Healthy Reefs for Healthy People
The Healthy Reefs for Healthy People Initiative (HRI) is an international, multi-institutional
effort that tracks the health of the Mesoamerican Reef, the human choices that shape it and
our progress in ensuring its long-term integrity. Launched in 2004, Blue Ventures has been an
official partner of HRI since 2012; data collected during expeditions are used in producing the
HRI biennial reef health report.
Southern Environmental Association
The Southern Environmental Association (SEA), based in Placencia, co-manages Gladden Spit
and Silk Cayes Marine Reserve and Laughing Bird Caye National Park. Together, Blue Ventures
and SEA are tackling the lionfish invasion coordinating the annual Placencia Lionfish
Tournament and monitoring lionfish populations to determine effective management
strategies.
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CHAPTER 3: INTRODUCTION TO CORAL REEFS
Coral Reefs
Coral reefs comprise less than 0.5% of the ocean floor, an area of 600 000 square miles, yet it is
estimated that more than 90% of marine species are directly or indirectly dependent on them.
They are home to a third of all the species in the ocean and include 4000 coral reef fish species,
which accounts for approximately a quarter of all marine fish species. Coral reefs are the most
productive ecosystems in the marine environment and are also able to fix large amounts of
carbon dioxide making them vital to the future health of the planet.
Structure of Corals Reefs
Coral reefs are often called the ‘rainforests of the sea’, and this comparison reflects the
enormous biodiversity that is immediately apparent to anyone who has had first-hand
experience of visiting a coral reef. Coral reef ecosystems are known for their spectacular
structures, colours and marine life that has the greatest diversity per unit area of any marine
ecosystem. Coral reefs are unique ecosystems and they are characterised by high productivity,
a great diversity of competitors and a complex set of interactions between all the species.
Although they are rich in biodiversity they are in fact fragile and it is only through their efficient
use of all available nutrients that enable them to maintain such a high degree of biodiversity in
the otherwise nutrient sparse tropical marine waters.
Where Reefs Exist
Reef-building corals are restricted in their distribution as a result of the algal-coral symbiotic
relationship. This relationship requires a consistent environment in which the temperature,
salinity and pH remain within a certain band. Therefore coral reef formation requires a sea
temperature that does not fall below 18 °C for any extended period. Most require a salinity that
ranges from 32 to 42 parts per thousand, and the water must also be clear to allow sufficient
light to penetrate. The corals’ requirement for high light for photosynthesis also explains why
most reef-building species are restricted to the euphotic (light penetration) zone,
approximately up to 70 m in depth. The number of species of corals on a reef declines with
depth, and as the light intensity diminishes the ability for corals to secrete limestone is reduced.
As a result of these environmental conditions that coral reefs require to develop, they are
found within the 20° surface isotherm, the tropical and semitropical waters. This limits their
distribution to a belt that runs around the earth between 30°o latitude north and south of the
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equator. The diversity of reef corals, the number of species, decreases in higher latitudes up to
about 30° north and south, beyond which reef corals are usually not found. The diversity of
coral species is also dependent on the ocean in which they are located. At least 500 reefbuilding species are known to exist in the waters of the Indo-Pacific region whereas the Atlantic
Ocean contains approximately 62 known species.
Ecosystem Interactions
Seagrass beds and mangrove forests are often important in the success, survival and stability of
coral reefs. The three ecosystems are closely linked and their interactions are often vital in the
continued health of the reef. The structure and function of each of these three ecosystems
vary:
Coral Reefs




Accrete CaCO3 (calcium carbonate)
Attenuate wave energy, protect shoreline
Offer refuge and food
Recycle Particulate Organic Material (POM)
Seagrass beds





Stabilise and bind sediment
Produce POM and DOM (dissolved organic matter)
Recycle and export nutrients
Produce floating leaf litter
Attenuates storm surges
Mangroves




Trap sediment
Reduce wave action
Buffer salinity changes (from sea and from freshwater runoff)
Act as a secondary nursery ground for fish and crustaceans
As well as having their own specialised associated organisms, mangroves and seagrass beds are
important nurseries for many species. Juvenile fish, crustaceans, molluscs and echinoderms
take advantage of the safer and more sheltered environment, with fewer predators, that the
mangroves and seagrass beds provide.
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A second important function of seagrass beds and mangrove forests in relation to reef health is
their ability to trap the sediment carried in rivers. This sediment discharge may otherwise run
the risk of damaging the reefs by sediment shading or smothering. As the trapped nutrients are
broken down a large volume of the oxygen in the water surrounding the mangroves is used.
This results in the mangroves having a low level of oxygen in the water surrounding them and
leaving only a thin layer of oxygen at the surface available for use by mangrove residents.
Furthermore, mangroves and seagrass beds are extremely important in the stabilisation of the
coastline by providing protection from storm damage and reducing the level of erosion.
Sea grass beds in addition to being nurseries are also used as feeding grounds for megafauna
such as turtles and manatees. They also act as a second stage of filter for any sediments which
have not been trapped in the mangroves, and soak up any excess nutrients that may promote
eutrophication (the proliferation of algae as a result of increased nutrients in the water) out on
the reef.
Regular problems for these habitats are almost exclusively anthropogenic in forms. Mangrove
wood is exceptionally dense and this makes it ideal for charcoal production. It is also a desirable
material for building and so in an area where building materials are scarce they are often
exploited. Seagrass beds are extremely delicate so one of the problems is propeller scarring,
where the wash of the propeller actually destroys the bed, fragmenting it and severely
restricting the movements of some species that live there.
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CHAPTER 4: DISTURBANCES TO CORAL REEFS
Disturbances to coral reefs can be the result of both natural and anthropogenic hazards and
threats. As human populations and coastal pressures increase coral reefs are becoming more
heavily exploited. Current estimates put 10% of coral reefs as degraded beyond recovery, with
a further 60% predicted to die by 2050 if current pressures and disturbances continue
unchecked.
The boundaries between natural and anthropogenic threats have become increasingly blurred
as the effects of natural disturbances are exacerbated by anthropogenic stresses, such as
climate change. Human activities can reduce the resilience of coral reefs and their ability to
recover from disturbances. They can also intensify the effects of natural disturbances, such as
increasing the frequency of disease outbreaks and tropical storms.
Storms and Cyclones
Extreme weather is one of the most obvious and major stresses to coral reefs as coral reefs
occur in the tropics, areas that are subjected to severe storms. During storm periods, not only
are the delicate coral skeletons broken, but increased sediment output from land erosion can
smother entire reefs.
Coral Bleaching
Corals and their symbiotic algae, zooxanthellae, are vulnerable to a variety of environmental
stresses that can disrupt the symbiotic relationship and cause bleaching - the loss of the
zooxanthellae and their photosynthetic pigment.
Stresses that can lead to coral bleaching include:






Elevated or decreased sea water temperature
Pollution
Sedimentation
Disease
Increased or decreased light levels
Fresh water flooding
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In 1998 a mass bleaching event occurred worldwide and in a report presented to the U.S. Coral
Reef Task Force in 1999, by the U.S. State Department warned: "In 1998 coral reefs around the
world appear to have suffered the most extensive and severe bleaching and subsequent
mortality in modern record. In the same year, tropical sea surface temperatures were the
highest in modern record, topping off a 50-year trend for some tropical oceans. Localised
stressors and natural variability alone cannot account for these events. The geographic extent,
increasing frequency, and regional severity of mass bleaching events are likely a consequence
of a steadily rising baseline of marine temperatures, driven by anthropogenic global warming.
Nutrient Enrichment
Nutrient enrichment in coral reefs normally occurs as a result of anthropogenic inputs, such as
sewage, or fertiliser and pesticide runoff. These anthropogenic inputs lead to excesses of
nutrients, nitrates and phosphates, in the water surrounding the coral reefs and can cause
eutrophication. Eutrophication results as the increase in the mineral and organic nutrient levels
of the waters promote a proliferation of plant life, and cause a sudden bloom of algae in the
previous nutrient poor tropical waters. The increase in algae reduces the dissolved oxygen
content of the water, which can lead to the suffocation of marine species. Eutrophication also
reduces the turbidity of the water and decreases the amount of light that can reach the corals.
The increase amounts of nutrients can also enhance the growth of other reef organisms, such
sponges and algae, which can out-compete the slower growing corals for space.
Overfishing and Destructive Fishing Practices
Increasing coastal populations have increased the pressure on marine resources. The majority
of coral reefs also occur in regions of high poverty and this has led to the overfishing and
unsustainable exploitation of fish and invertebrate populations. Overfishing can be particularly
damaging to populations of slow maturing species, such as sharks, groupers and marine turtles.
Anchor and Diver Damage
Physical damage to the reef can occur as a by-product of large numbers of people using the reef
or through targeted extraction of items from the reef. Dive boats anchoring repetitively at
certain dive sites can cause huge damage but permanent moorings prevent this. Accidental
damage also occurs as a result of divers who are unable to maintain neutral buoyancy or swim
too close to the reef.
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CHAPTER 5: FISH BIOLOGY AND IDENTIFICATION
The superclass Pisces is divided into two classes, the Osteichthyes (the bony fish) and the
Chondrichthyes (the cartilaginous fish).
Class Osteichthyes - Bony Fish
Figure 1.1 Typical osteichthyes features
The bony fish (Figure 1.1) comprise the largest class of the vertebrates, with over 20,000
species worldwide, of which 7,000 are coral reef fish species. The bony fish have calcified
skeletons, making their bones much harder than the cartilage skeleton of the Chondrichthyes.
The bony fish have great manoeuvrability and speed, as well as highly specialised mouths
equipped with protrusible jaws. Most bony fish have a swim bladder, a gas-filled internal pocket
that can be inflated and deflated at will, in order to maintain neutral buoyancy and to stay
upright. The majority of fish propel themselves by sweeping their caudal (tail) fin from side to
side, whilst the dorsal fin maintains the vertical axis of the fish and prevents rolling. Fish have a
well-developed sense of smell and some species possess barbels (Figure 1.2), which are covered
in taste receptors and used to locate food.
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Figure 1.2 Barbels (circled in red) on a spotted goatfish, Pseudupeneus maculatus
Fish respire by passing water over their gills, through which they absorb dissolved oxygen, and
are able to move an estimated 74% of the dissolved oxygen from the water. Their skin is
covered in mucus glands and is protected by dermal scales. A hard bony plate known as the
operculum protects the gills, a feature absent in the elasmobranchs (Chondrichthyes).
Osteichthyes also possess a line of small perforated tubes, called the lateral line, that run just
under the skin along the midlateral part of the body, and are often visible. These tubes detect
minute vibrations in the water, allowing fish to sense the movement and motion of other
animals in the water.
Class Chondrichthyes - Cartilaginous fishes
Figure 1.3 Typical cartilaginous fish features (shark species)
The Chondrichthyes (sharks and rays) (Figure 1.3) have skeletons that are composed of
cartilage. Unlike the bony fish they have no internal swim bladder to keep buoyant, but instead
have a greatly enlarged oily liver running the length of their body. Oil is lighter than water and
serves to make the animal more buoyant. Sharks must continually swim to remain elevated in
the water column and their fins provide hydro-dynamic lift in a similar fashion to the wings of
an aeroplane. Males are distinguished from females by two long finger-like fins behind their
pelvic fins, known as claspers, which are used for mating. The skin of the Chondrichthyes is not
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covered in scales but is either smooth or covered in many microscopic teeth known as dermal
denticles, which serve to break the water tension as they swim through the water.
Sharks have a highly developed sense of smell and this allows them to detect minute traces of
scent in the open ocean to locate food. Sharks sight varies from species to species although all
have excellent low light vision because of a light reflective membrane on the retina. This results
in light being reflected back through the eye allowing them to see very well at dusk and night
time when these animals normally hunt. Sharks and rays have electro-receptors that are
sensitive to the magnetic fields produced by other living animals and allow sharks to close a
membrane over their eye for protection in the last few moments before they strike. These
finely tuned senses allow sharks to be very effective predators in murky and low levels of light.
Reproduction in the Chondrichthyes can take one of three forms. Once the eggs are fertilised
they develop either encased in a hard envelope outside the parent’s body (ovoviviparity) or
encased eggs develop within the parent’s body (oviparity), or finally eggs develop attached to a
placenta-like structure within the parent and are born live (viviparity).
Introduction to fish behaviour
Diversity
The variety of niches provided by coral reefs, mangroves and seagrass beds enable a diverse
range of fish to inhabit these ecosystems. The availability of resources supports corallivores
(e.g. butterflyfish species), herbivores (eg. surgeonfish species), planktivores (e.g. whale sharks)
and invertivores (e.g. the southern stingray). Additionally, the architectural complexity of the
reef structure provides a habitat suitable for ambush predators such as the moray eels and
groupers.
Fish behaviour can be the first key to accurate identification of fish families and species. For
example, damselfish species, such as the bicolour damsel and yellowtail damsel, are herbivores,
and as such will be closely associated with the reef substrate. However, blue chromis, also from
the damselfish family, are planktivores and therefore swim slightly above the reef in the water
column itself.
Schooling
Schooling is another behaviour that is commonly exhibited by only certain species. Visually
similar fish species can be positively identified by their tendency to school. For example, the
blue chromis and creole wrasse share a similar colouration, shape and size; but creole wrasse
often form large schools, whereas blue chromis will only aggregate in small groups. The reasons
for schooling can range from cooperative hunting, to mating and overwhelming territories.
Schooling behaviour can be classified in three categories: polarised schools, aggregations and
non-polarised schools. Polarised schools occur when the fish act as a single unit, for example
Creole wrasse. Aggregations occur when multiple species are attracted to the same resource,
for example, French grunts, bluestriped grunts and white grunts. Non-polarised schools occur
when the same fish species aggregate close together.
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Territoriality
Fish species are usually more aggressive to other individuals of the same species or similar
species competing for same resources. This occurs because species that share similar niches
have similar needs, and territorial behaviour may change depending on the abundance of
resources. Territory sizes vary from species to species, and the size or location of the territory
may change depending on time of day. Triggerfish species have a conical shaped territory.
Certain fish exhibit territorial behaviour, such as damselfish which ’farm’ algae. In this case, a
seemingly inquisitive fish may actually be defending its territory against a diver. Nesting fish
may also display territoriality, and when male Sergeant Major damselfish guard their nest their
colouration can become more strongly blue.
Colouration
Many fish species utilise colouration as a means of crypsis or mimicry. Ambush predators, such
as groupers, are camouflaged. The markings on a Nassau grouper serve to break up the outline
of the fish, concealing it from its prey; whilst scorpionfish mimic dead coral and rocks as a
disguise. Pelagic species such as jacks are silvery in colouration as this serves the best
camouflage against the backdrop of the open ocean.
Symbiosis
Symbiotic relationships are commonly found throughout the reef between many fish species,
and also between fish species and other groups of organisms, such as the crustaceans.
Symbiosis can be one of three forms; commensalism, mutualism or parasitism. Commensalism
occurs when the one species gains from the relationship and the other species is not affected
either negatively or positively. For example, remoras have a specially adapted plate on their
head allowing them to attach to much larger fish species, from which it gains a free ride,
protection and food scraps. The host remains unaffected.
Mutualism occurs when both species gain from the relationship. For example, cleaner gobies
will feed on parasites located on larger fish. In this case, both parties benefit as the cleaner
receives a free meal and the host fish benefits from improved health. Parasitism occurs when
the host species is negatively affected by the parasitic species. For example, parasitic isopods
attach to the operculum of fish and feed on their blood.
Reproduction, spawning and nesting
The majority of fish species release eggs that are fertilised externally. Many species are
broadcast spawners where the eggs are released into the open sea, where fertilisation will
occur, and are not cared for subsequently. Some species lay their eggs in nests and will guard
them until they hatch, such as many damselfish species. Fertilised eggs hatch into larvae and go
through several stages of development until they become juveniles. Juvenile fish often have
distinct colouration and patterns from their parents.
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Sequential hermaphroditism
Many fish species are able to change sex during their lifetime, and are known as sequential
hermaphrodites. Wrasse and parrotfish species exhibit sequential hermaphroditism (Figure
1.4). This occurs when the largest initial phase female of the group changes sex, into a terminal
phase male. Species that change from female to male are known as protogynous
hermaphrodites. Terminal males are always dominant over initial phase adults, both males and
females. The presence of a terminal male will inhibit the changing of any other initial females in
the group. Initial phase males are unable to change into terminal males. Initial phases tend to
display dull colouration and patterning, whilst terminal phases are often markedly different
with vivid colouration.
JUVENILE PHASE (MALE/FEMALE)
INITIAL PHASE (FEMALE)
TERMINAL PHASE (MALE)
INITIAL PHASE (MALE)
Figure 1.4 Sequential hermaphroditism shown by the stoplight parrotfish
CHAPTER 6: COMMON FISH FAMILY IDENTIFICATION
Identifying fish families
When confronted with the large numbers of fish on a coral reef it is easy to feel overwhelmed
with trying to identify families, let alone individual species. It is important to not rely too heavily
on the colour of fish when trying to identify fish families but instead to observe their size, body
shape and behaviour closely. The colour of fish is only really useful in identifying individual
species within a family and even then it can be difficult as species colour can be different for
each sex or can change as they age. Some fish species also mimic the colour of other species
making it even more important that anyone trying to identify fish is familiar with the body
shape of each fish family.
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Scaridae – Parrotfish
The parrotfish (Figure 2.1) closely resemble wrasse but have teeth fused into beak-like plates,
which is not only the origin of their name but also the defining characteristic of the family. They
are some of the most important reef herbivores in the Caribbean, as their diet primarily
consists of algae, although they do also feed on coral. Parrotfish crush algae-encrusted rock and
live coral with their beak-like teeth before digesting it. This causes parrotfish to excrete plumes
of sand, a second distinguishing characteristic of the family, and makes them the biggest
producers of sand on coral reefs. Similar to the wrasse family, the parrotfish also swim in a
flapping motion using their pectoral fins. Individual parrotfish species can also be difficult to
identify because they also change colour with age and sex.
During the day parrotfish are seen swimming alone or small schools around the reef, biting
chunks of rock or coral with their teeth and excreting puffs of sand. At night parrotfish sleep
wedged in holes and crevices on the reef; some species can surround themselves with a mucus
cocoon that may help to protect them from predators by hiding their scent.
Figure 2.1 Queen parrotfish, Scarus vetula (20 – 50 cm)
Labridae – Wrasse
Wrasse (Figure 2.2) are among the most diverse group of fishes in both size and body shape,
which also makes them one of the hardest families to identify species correctly. Typically
wrasse have elongate bodies, terminal mouths (usually with thickened lips), and one or more
pairs of protruding canine teeth. Wrasse have a distinct swimming pattern, which they share
with the parrotfish family, using primarily their pectoral fins in a flapping motion. Wrasses also
generally have a single, unnotched dorsal fin. Individual wrasse species can be particularly
difficult to identify because most species have complex and brilliant colour patterns that
change with growth or sex.
Most wrasse are carnivores of benthic invertebrates or fishes although some are planktivores,
corallivores, or feed on ectoparasites on other fishes (cleaner wrasse). Wrasse are normally
seen swimming rapidly around the reef alone or in small groups.
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Figure 2.2 Spanish hogfish, Bodianus rufus (8 – 50 cm)
Pomacentridae – Damselfish
Damselfish are a large family with over 100 species and are some of the most commonly seen
reef fish. They are small, and generally no larger than 15 cm. They have moderately deep
compressed bodies, continuous dorsal fins, and small terminal mouths. Some damselfish
species are highly territorial and will confront divers underwater. Many species are often seen
in medium sized shoals living closely associated with a coral head which they retreat into if
approached. All lay demersal eggs that are
defended by males.
Figure 2.3 Yellowtail damselfish, Microspathodon chrysurus (3 - 15 cm)
Chaetodontidae – Butterflyfish
The butterflyfish are among the most colourful and conspicuous reef fish. They have highly
compressed, disk-like bodies covered with small scales, a small protractible mouth with small
brush-like teeth, and a long continuous dorsal fin. They are typically diurnal and have minimal
home-ranges. Most species of butterflyfish live closely associated with coral and feed on coral
polyps. Butterflyfish also feed on small invertebrates, fish eggs and filamentous algae.
Butterflyfish tend to be gonochoristic1 with most species mating in pairs for years, if not for life,
and are therefore often seen in pairs on the reef. Many species of butterflyfish have a dark
stripe that camouflages their eyes, and juveniles are often a different colour and pattern to
adults. Butterflyfish tend to be timid and are likely to swim away from divers.
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Figure 2.4 Foureye butterflyfish, Chaetodon capistratus (10 - 20 cm)
1
Pomacanthidae – Angelfish
Angelfish (Figure 2.5) have a compressed body with a small mouth. The key identification
feature of the angelfish family is that they all possess a spine that extends backwards from the
front of their operculum (gill plate). Juveniles and adults often have strikingly different colour
patterns. They are active by day and generally seek shelter in caves and crevices at night. Most
species feed on sponges, some soft bodied invertebrates, algae and fish eggs, whilst other
species feed on small invertebrates and filamentous algae. Angelfish tend to be quite shy and
many species will retreat into crevices and under coral when approached by a diver. Angelfish
are usually observed as individuals or pairs.
Figure 2.5 French angelfish, Pomacanthus paru (10 – 40 cm)
1
Those species with sexes separate, the male and female reproductive organs being in different
individuals.
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Acanthuridae – Surgeonfish
Surgeonfish (Figure 2.6) have ovate or elongate compressed bodies, small terminal mouths and
a continuous dorsal and anal fin. The distinguishing feature of this family, and the origin of their
common name, is the sharp blades which sit on each side of the caudal peduncle (the area
between the body and the tail). These blades act as a defence against predation. Surgeonfish
are some of the most important reef herbivores in the Caribbean as they graze on all types of
algae. Their gizzard like stomach uses sand to grind the algae to aid digestion.
Figure 2.6 Ocean surgeonfish, Acanthurus bahianus (10 - 25 cm)
Serranidae – Groupers, Hamlets and Soapfish
Groupers (Figure 2.7), hamlets and soapfish are a large and diverse family of reef fish. The
family all share a distinctively shaped pupil. Groupers are large, robust-bodied bottom dwellers
with large, down-turned mouths that they use to suck in prey. Groupers are normally seen as
solitary individuals and are voracious predators of crustaceans, fishes, and cephalopods. Some
species of grouper hide from divers and the most seen of an individual is its tail disappearing
under a rock, whilst others rest on coral heads and rock. Groupers also like to rest in caves and
holes. Large species may live for several decades and reach weights of up to 400 kg and 3 m in
length. Many species are sequential hermaphrodites (first female then male) and if larger fish
are harvested the population could contain a disproportionate number of smaller females.
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Figure 2.7 Black grouper, Mycteroperca bonaci (50 – 150 cm)
Balistidae – Triggerfish
Triggerfish (Figure 2.8) are characterised by a first dorsal fin with three spines that can lock
upright and a swimming motion that involves undulating the second dorsal fin and anal fin
simultaneously.
They have a relatively deep, compressed body with eyes set high on the head, a small terminal
mouth and large snout with sharp teeth. Triggerfish are carnivores of urchins and other
echinoderms, corals, fish, molluscs and crustaceans. Most species lay demersal eggs which are
often viciously guarded by at least one of the parents and they will protect a cone shaped area
that radiates upwards from their eggs. Most species of triggerfish are seen solitary, often in
sandy patches, but some are found in large schools such as the black durgon (Melichthys niger).
Figure 2.8 Black durgon, Melichthys niger (20 – 40 cm)
Monocanthidae – Filefish
Filefish (Figure 2.9) are very similar to triggerfish but have only one long, prominent dorsal
spine compared to the three shorter dorsal spines on the triggerfish. Filefish also have more
compressed, thinner bodies. Filefish lack large obvious scales. They are normally seen solitary
or in pairs swimming close to the reef.
Figure 2.9 Whitespotted filefish, antherhines macrocerus (10 – 40 cm)
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Lutjanidae – Snappers
Snappers (Figure 2.10) are medium to large robust fish that are commonly seen in schools
swimming off the reef. They have continuous dorsal fins and large coarse scales. All but one
species of snapper in the Caribbean has a square-shaped tail, with only one species possessing
a forked tail. Most species are predators of crustaceans and smaller fish. Many smaller species
school by day, and disperse to feed on benthic invertebrates at night, whilst some larger
species tend to be solitary.
Figure 2.10 Grey Snapper, Lutjanus griseus (35 - 45 cm)
Haemulidae – Grunts
Grunts (Figure 2.11) are most easily confused with snappers. Most grunts have a steeply sloping
forehead and some have thickened lips. Unlike snappers, all grunts have a shallowly forked tail.
Grunts are normally seen in small groups or solitary, swimming slowly near the reef, however,
in the backreef large multispecific aggregations can form. Grunts generally feed at night on
benthic invertebrates and small fish.
Figure 2.11 Bluestriped grunt, Haemulon sciurus (15 - 25 cm)
Scorpaenidae – Scorpionfish
Scorpionfish and lionfish both have venomous fin spines. Scorpionfish are well-camouflaged
fish that are covered in appendages and tassels, and remain motionless resting on coral heads,
rocks or the substrate waiting for prey. Scorpionfish will dart away from their resting place if a
diver approaches too close and are often not observed until this point. Some have brightly
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coloured undersides or parts of their pectoral fins, which may be flashed as a warning to
potential predators.
Lionfish have long spines on their dorsal and pectoral fins (Figure 2.18). They have a large spiny
head and a bony ridge on their gill plate. Lionfish spread their pectoral fins out like a net to trap
prey. They have venomous spines on their pelvic, dorsal and anal fins. Lionfish are an invasive
species in the Caribbean, introduced from the Pacific into the Atlantic in 1983. They were first
recorded in Belize in 2008 and have since become well established throughout the country.
They are voracious predators consuming juvenile fish and shrimp species.
Figure 2.18 Lionfish, Pterois volitans
Carangidae – Jacks
Jacks (Figure 2.20) are medium to large silvery fish. They are fast-swimming pelagic fish so are
generally observed swimming in the deeper water off the reef. They have two dorsal fins, a long
pectoral fin and a highly forked tail fin. They are often seen in schools and are an economically
important food fish.
Figure 2.20 Bar jack, Carangoides ruber (30 – 100 cm)
Sphyraenidae – Barracuda
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Barracudas (Figure 2.21) are elongate fish with silvery bodies. They have long, pointed heads
with large down-turned mouths with numerous sharp teeth. Barracudas also have two widely
spaced dorsal fins. They are often seen solitary but more often they are seen in schools. They
very rarely attack divers but it is reported that they may sometimes be attracted to shiny,
silvery objects in the water.
Figure 2.21 Great barracuda, Sphyraena barracuda (70 -100 cm)
Scombridae – Mackerel
Mackerels (Figure 2.22) are elongated, silver, fast swimming predators of the open sea that
only occasionally pass over reefs. They have two dorsal fins that fold into grooves. Between
their dorsal fin and tail and their anal fin and tail they have small finlets, to increase
maneuverability and balance. They have a strong, forked tail signifying the speed at which they
pass through the water. Tunas and ceros are members of this family.
Figure 2.22 Cero, Scomberomorus regalis (50 – 90 cm)
Elopidae - Tarpon
Tarpon (Figure 2.23) are a commercially important fish family. They have a flexible and
acrobatic body enabling them to work their way off of a fish-hook, which makes them appealing
to sport fishermen, although in Belize they are strictly catch and release. Tarpon can live in
hypoxic2 water as they possess a modified lung-like swim bladder. They use their upturned
mouths to gulp air at the surface. Tarpon can be very long-lived and grow to a very large size.
They commonly inhabit the shallow area of mangrove habitats.2
22 2
An aquatic system with a low concentration of oxygen (1 – 30% saturation). A healthy
aquatic system is normally 80% oxygen saturation.
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Figure 2.23 Tarpon, Megalops atlanticus (60 – 120)
Gerreidae - Mojarras
Mojarras (Figure 2.25) are normally found in seagrass beds and mangroves and are the most
popular fish to eat in Sarteneja. Mojarras have bright, reflective, obvious scales. They have a
laterally compressed body, with highly protrusible mouths and deeply forked tail. Rarely on
reefs, they inhabit shallow surge-swept sandy shorelines, rubble, grass or mud flats where they
feed on small invertebrates. Several species are difficult to distinguish, but careful attention to
subtle markings and body shapes usually provides a correct identification.
Figure2.25Yellowfinmojarra,Gerrescinereus (20–40cm)
CHAPTER 7: COMMON MEGAFAUNA IDENTIFICATION
Elasmobranchs (sharks and rays)
Bull Shark (Carcharhinus leucas)
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The bull shark (Figure 3.1) is a stocky, heavy bodied shark. They have a short, blunt, rounded
snout and small eyes. Bull sharks have a large triangular, pointed first dorsal fin, with a wide
base. Corozal Bay is a nursery ground for bull sharks.
Figure 3.1 Bull shark, Carcharhinus leucas (maximum 4 m)
Caribbean Reef Shark (Carcharhinus perezi)
The Caribbean reef shark has a grey upper half of its body, with a fading white underside. They
have rounded snout and a dusky tip on their anal fin, with a sharply pointed first dorsal fin and
long, narrow pectoral fins.
Figure 3.2 Caribbean reef shark, Carcharhinus perezi (maximum 3.5 m)
Nurse Shark (Ginglymostoma cirratum)
The nurse shark (Figure 3.3) is the most commonly seen shark in the Bacalar Chico Marine
Reserve. Often seen ‘resting’ on the sandy floor beside coral bommies and under overhangs,
they are able to actively pump water over their gills. Nurse sharks have barbels on their snout
and flattened bellies, optimised for feeding on benthic invertebrates. They have a low front
dorsal fin and second dorsal fin of equal size.
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Figure 3.3 Nurse shark, Ginglymostoma cirratum (maximum 4.5 m)
Blacktip Shark (Carcharhinus limbatus)
The blacktip shark (Figure 3.4) is distinguished by black edging on its pectoral, pelvic, dorsal and
lower lobe of the caudal fin, though this fades to become more indistinct with age. A second
distinguishing feature is the presence of a white streak on its flank, extending from the caudal
peduncle, above the anal fin and toward the centre of the body. They also have a pale to white
anal fin.
Figure 3.4 Blacktip shark, Carcharhinus limbatus (maximum 3 m)
Whale Shark (Rhincodon typus)
The whale shark (Figure 3.5) is the largest fish in the sea. They are easily identified by the large
white spots covering their grey body. Whale sharks have a large, broad mouth and a flattened
head; and are planktivores.
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Figure 3.5 Whale shark, Rhincodon typus (maximum 15 m)
Tiger Shark (Galeocerdo cuvier)
The tiger shark (Figure 3.6) has dark bars and blotches all over its body, resembling stripes. They
have a large head, blunt snout and wide mouth. The first dorsal fin on a tiger shark is broad and
larger than second dorsal fin. They can be potentially very dangerous.
Figure 3.6 Tiger shark, Galeocerdo cuvier (maximum 8 m)
Great Hammerhead Shark (Sphyrna mokarran)
The great hammerhead shark (Figure 3.7) has a very large front dorsal fin. Their head protrudes
in a large hammer shape, with a straight leading edge. The rear edge of their pelvic fin is
curved. Great hammerhead sharks are usually solitary.
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Figure 3.7 Great hammerhead shark, Sphyrna mokarran (maximum 6m)
Scalloped Hammerhead Shark (Sphyrna lewini)
The scalloped hammerhead shark (Figure 3.8) in contrast to the great hammerhead shark has a
deeply scalloped hammer on the front of its head. The pelvic fin has a straight rear edge.
Scalloped hammerhead sharks have a second dorsal fin smaller than their anal fin.
Figure 3.8 Scalloped hammerhead shark, Sphyrna lewini (maximum 5 m)
Caribbean Round Stingray (Himantura schmardae)
The Caribbean round stingray (Figure 3.9) is the second most commonly sighted stingray in
Bacalar Chico Marine Reserve. They often come close to shore feeding on the invertebrates on
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the seagrass beds. The side of the head is continuous with the pectoral fins. They can be
identified by their entirely circular shaped disc-like bodies. They also have a whip like tail.
Figure 3.9 Caribbean stingray, Himantura schmardae (maximum 1.2 m)
Southern Stingray (Dasyatis Americana)
The Southern stingray (Figure 3.10) is the most commonly sighted stingray in Bacalar Chico
Marine Reserve. They are generally sighted in shallow backreef areas where they will often
cover their bodies in sand leaving only their eyes uncovered. They are easily identified from the
Caribbean round stingray by their pointed snout and tips of wings. Southern stingrays have a
kite shaped body.
Figure 3.10 Southern stingray, Dasyatis Americana (maximum 2 m)
Spotted Eagle Ray (Aetobatus narinari)
Spotted eagle rays (Figure 3.12) are occasionally sighted in Bacalar Chico Marine Reserve. They
can be easily distinguished from the other ray species by the numerous white spots and circular
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marks over their dark backs. Spotted eagle rays have a pronounced head, a long, thin tail and
angular pectoral fins.
Figure 3.12 Spotted eagle ray, Aetobatus narinari (maximum 2.5 m)
Yellow stingray (Urolophus jamaicensis)
Yellow stingray have numerous pale spots and blotches on yellowish brown coloured body
(Figure 3.13). The snout and tips of pectoral fins rounded and the tail is stout with venomous
spines near the end. Its maximum diameter is 35cm.
Figure 3.13 Yellow stingray Urolophus jamaicensis (maximum 35cm)
Lesser Electric Ray (Narcine bancroftii)
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The lesser electric ray is grey to brown colour and may have dark blotches and/or spots (Figure
3.14). These nearly circular rays have a short tail with thick base. The tail has two dorsal fins of
equal size. Maximum diameter is 45cm.
Figure 3.14 Lesser electric ray Narcine bancroftii (maximum 45cm)
Turtles
All species of marine turtle are classified by the IUCN as vulnerable, endangered or critically
endangered because of the overharvesting of their eggs, accidental death via bycatch and boat
traffic, direct exploitation of adults for their meat and shell, and habitat and nesting disruption.
The most accurate clues for identification are the patterns on the top of their shells (Figure
3.14). The shell is made up from central/bridge plates (large plates running down the centre of
the shell), costal plates (a single row of plates paralleling each side of the central plates) and
scutes (small plates on the shell’s edge). The size of the tail on a turtle can be used to identify
its sex once mature. A male turtle will have a tail longer than its rear flippers, whilst a female
turtle will have a tail shorter than its rear flippers.
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Figure 3.14 Turtle identification guide
Hawksbill Turtle (Eretmochelys imbricata)
The hawksbill turtle (Figure 3.14) has an overhanging upper beak (hence the name hawksbill),
though this should not be used as the sole feature for identification. The hawksbill is one of the
most commonly sighted turtles in Bacalar Chico Marine Reserve, seen both on the forereef and
backreef. They can be accurately distinguished from the green turtle by the two pairs of scales
between their eyes. They often have brown shells, with yellow-brown-like markings. The rear
border plates on a hawsksbill turtle have a serrated edge, and the shell plates overlap.
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Figure 3.14 Hawksbill turtle, Eretmochelys imbricata (maximum 1.2 m).
Green Turtle (Chelonia mydas)
Green turtles (Figure 3.15) often have brown shells with olive shadings, which gives them a
chequered pattern. They have only one pair of scales between the eyes, distinguishing them
from the hawksbill turtle. The shell plates of a green turtle do not overlap and the margin of the
carapace is not serrated. Green turtles are the second most commonly sighted turtles in Bacalar
Chico.
Figure 3.15 Green turtle, Chelonia mydas (maximum 1.5 m)
Loggerhead Turtle (Caretta caretta)
Loggerhead turtles (Figure 3.16) are the second largest marine turtle. Sighted rarely in Bacalar
Chico Marine Reserve they have a large blunt head and powerful jaws, which easily
distinguishes them from the other turtle species found in this part of Belize. Loggerheads have
a steeply domed carapace with a reddish, brown shell.
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Figure 3.16 Loggerhead turtle, Caretta caretta (maximum 2 m)
Leatherback Turtle (Dermochelys coriacea)
Leatherback turtles (Figure 3.17) are the largest marine turtle. They possess no shell plates;
instead their back is covered by a tough leather-like skin, allowing them to dive to great depths.
They are also the only marine turtle to thermoregulate, enabling them to inhabit all of the
world’s oceans.
Figure 3.17 Leatherback turtle, Dermochelys coriacea (maximum 1.8 m)
Olive Ridley Turtle (Lepidochelys olivacea)
The olive ridley turtle (Figure 3.18) are listed as vulnerable by the IUCN, and are very rare in
Bacalar Chico. They are olive (dull) in colour and are found in tropical open waters.
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Figure 3.18 Olive Ridley Turtle Lepidochelys olivacea
Mammals
Bottlenose Dolphin (Tursiops truncates)
Bottlenose dolphins (Figure 3.18) are a light blue to slate grey colour, with a paler underside.
They are the most commonly sighted dolphin in Bacalar Chico. They have a pronounced beak
and a rounded forehead. Bottlenose dolphins can be identified from the Atlantic spotted
dolphin by their slightly hooked, tall dorsal fin. They are normally found in small groups.
Figure 3.18 Bottlenose dolphin, Tursiops truncates (maximum 3m)
Atlantic Spotted Dolphin (Stenella frontalis)
The Atlantic spotted dolphin (Figure 3.19) is smaller in size than the bottlenose dolphins. They
are a grey to black in colour with pale spots. Atlantic spotted dolphins are nearly always seen in
large groups.
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Figure 3.19 Atlantic spotted dolphin, Stenella frontalis (maximum 2.5 m)
West Indian Manatee (Trichechus manatus)
The West Indian manatee (Figure 3.20) is the largest species of manatee. The population in
Belize has been estimated at around 800 individuals. There are concerns that fragmentation of
this population from the population in Florida, due to overharvesting in Mexico, may lead to
inbreeding and a decrease in genetic diversity, further threatening the future of this species.
They have grey skin colour and a large head with mobile lips covered in bristles. Manatees are
easily spotted by their large paddle shaped tails, which make a circular ripple on the surface of
the water.
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Figure 3.20 West Indian manatee, Trichechus manatus (maximum 3.5 m)
CHAPTER X: INTRODUCTION TO PLANTAE AND
IDENTIFICATION
Algal species are very important for reef health. Algae and coral compete for space in reef
habitats, and fast-growing algae will outcompete coral if grazing of algae is not high enough or
eutrophication enhances algal growth rates. This can lead to an algal phase-shift3. Calcareous
forms of green algae (in particular Halimeda spp.) contribute significant amounts of calcium
carbonate to marine sediments found in seagrass beds, and on coral reefs and beaches.
Calcareous red algae (crustose and articulated coralline algae) play an important role in the reef
building process by adding calcium carbonate to the reef and aiding in cementation. Most
herbivore groups are able to feed on turf algae, while fewer feed on macroalgae and even
fewer on coralline algae. When herbivory is reduced or removed, turf algae are able to colonise
on and around coralline algae and once established they begin to trap sediment and kill
underlying coralline algae. When grazing intensity increases, turf and macroalgal cover should
decrease.
Turf algae
Turf algae (Figure 4.1) are formed from tiny filaments, with canopy heights of less than 1 cm.
They are often able to recover rapidly after being partially consumed by herbivores.
Surgeonfish, damselfish and parrotfish feed on turf algae. Turf algae are capable of trapping
ambient sediment and may outcompete corals for space if herbivory rates are low. They are
easily identified as a moss- like covering over rocks and sand.
Figure 4.1 Turf algae
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Fleshy Macroalgae
Fleshy macroalgae (Figure 4.2), unlike turf algae, has a clear growth form. The blades of
macroalgae are larger than turf algae, with a canopy height usually greater than 1 cm.
Figure 4.2 Fleshy macroalgae
Dictyota spp.
Dictyota spp. (Figure 4.3) are branched algae which fork near their rounded or pointed ends. It
forms mats of dense, loose-packed, flat leaves that overgrow the substrate. Torn algae can be
misidentified as Dictyota so it is important to look at the structure as a whole.
Figure 4.3 Dictyota spp. (4 – 18cm)
Lobophora spp.
Lobophora spp. (Figure 4.4) are an encrusting fan leaf algae. The thin fan-shaped leaves are
often overlapping. Lobophora spp. only ever grow flat to the substrate and are found at depths
of 4 m – 100 m. They can be commonly misidentified with a species of macroalgae, which forms
lobe-like, upright leaves.
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Crustose coralline algae (CCA)
Crustose coralline algae (Figure 4.6) play two important roles in the coral reef community,
firstly, by contributing calcium carbonate to reef structure, and secondly, by facilitating the
settlement of coral recruits. This occurs when the CCA provides a clean substrate for the coral
to then grow over. Looking like paint splashed over the rock substrate, CCA is found in shades
of pink, purple, red and orange. It is also able to form brittle plates, growing actively away from
the substrate upon which it initially encrusted.
Figure 4.6 Crustose coralline algae (CCA)
Articulated coralline algae
Articulated coralline algae (Figure 4.6) are branching calcareous red algae. It is easily identified
by its twig-like structure, and is frequently seen growing in bunches off the substrate and within
crevices formed by submassive and foliose corals.
Figure 4.7 Articulated coralline algae
4.4. Seagrass
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Seagrass is an angiosperm (a true flowering plant) and has leaves not blades (Figure 4.8).
Instead of a holdfast and stipe as seen in the algae species, seagrass has an underground root
system. Within the leaves there are visible veins running up the leaves. Seagrass beds are a very
important habitat for invertebrates, fish and bird species (Figure 4.9). It is also the sole food
source for manatees and forms the primary part of an adult green turtle’s diet. It also provides
protection against coastal erosion.
Figure 4.8 The differing features of seagrass and algal species
Figure 4.9 Seagrass
4.5. Cyanobacteria/Blue green algae
Cyanobacteria/blue green algae (Figure 4.10) are commonly known as ‘troll’s hair’. The thin
filaments resemble a coarse hair-like clump or mat on the substrate. Most commonly found in
shades of reddish brown, it is also seen in a blue-green form. Cyanobacteria can form rapidly
expanding dense mats, threatening nearby corals by shading and overgrowth
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Figure 4.10 Blue green algae/Cyanobacteria
CHAPTER X: COMMON INVERTEBRATE PHYLA AND
IDENTIFICATION
Invertebrates account for 95% of species in the Animal Kingdom. The Animal Kingdom has just
over a million scientifically described species categorised into thirty-two phyla. The phylum
Chordata, which includes all fish, birds, and mammals, only contains around 45,000 (3%)
species, of which only 4,000 (0.03%) are mammals. The remaining phyla are comprised of
invertebrate groups. Some invertebrates are "keystone species" playing particularly important
roles in the maintenance of biotic communities. Coral reefs are perhaps the most dramatic
example, providing a wide range of niches for a diversity of plants and perhaps one-third of all
fish species. Here we will take a brief look at some of the most commonly seen reef
invertebrates.
Phylum Porifera (Sponges)
Sponges are the oldest living group of metazoan (multi-cellular organisms) with over 9000
described species to date. They first appear in the fossil record over 600 million years ago
during the Late Precambrian period. Sponges have simple body plans that function at the
cellular level. They have
neitherorgansnoradigestivecavityormouthandlackbothmusclesandnerves. Spongesaresessile
filter feeders and they have tiny inhalant pores, called ostia, in their outer walls through which
water is drawn (Figure 5.1). Cells in the sponge walls, called choanocytes, filter bacteria and
food particles from the water. Water flowing through sponges therefore provides food and
oxygen and acts as a means for waste removal. These cells also have whip-like flagellum which
drives the flow of water into the sponge. The flow of water through the sponge is unidirectional
and is pumped out of the body through exhalent holes. The volume of water passing through a
sponge can be enormous, up to 20,000 times its volume in a single 24 hour period.
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Figure 5.1 The ostia (inhalant pores) of a sponge, through which water is filtered, are
clearly visible
Sponges can trap roughly 90% of all bacteria in the water they filter. Some sponges also
harbour symbionts such as green algae, dinoflagellates, or cyanobacteria, from which they also
derive nutrients.
Sponges can reproduce asexually and sexually. Most sponges that reproduce by sexual means
are hermaphroditic and produce eggs and sperm at different times. Sperm are frequently
"broadcast" into the water column and are subsequently captured by female sponges of the
same species. Once the larvae are in the water column they settle and develop into juvenile
sponges. Asexual reproduction is through budding or fragmentation.
Sponges on the reef provide homes for a large diversity of other organisms, including shrimps,
crabs, barnacles, worms, brittlestars, sea cucumbers, other sponges, cyanobacteria, and lightloving microbes. Sponges appear to suffer little predation, only being fed on by nudibranchs
and certain species of fish and turtle. This is thought to be due to the complex protective
compounds produced by sponges as a by-product of their daily metabolism. Several of these
sponge compounds are shown to be active against certain tumour cell types and highlights the
possible medicinal resource of the Porifera.
Sponges can develop into diverse life forms, ranging from large barrels (Figure 5.2), to
encrusting sheets (Figure 5.3). The encrusting sheets can be extremely thin often resulting in a
clear view of the dead coral beneath, meaning that care should be taken when identifying.
Their structure is supported by a skeleton composed of an organic substance called spongin, or
they may have calcareous or siliceous skeletons composed of chambers, or more commonly
rod-like branched elements called spicules.
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Figure 5.2 Erect sponge
Figure 5.3 Encrusting sponge
Phylum Mollusca
The molluscs are a diverse group of over 160,000 different species, of which about half are
marine. The phylum Mollusca is divided into eight classes but there are three major classes, the
gastropods, which comprise 80% of all living molluscs, the bivalves and the cephalopods.
Although the members of this phylum range in body shape from the gastropod snails to the
giant squid there several key features which define the molluscs. The body is soft, unsegmented
and bilaterally symmetrical usually with a definite head. The ventral or lower part of the body
wall is often specialised into a muscular foot and used chiefly for locomotion. The dorsal body
wall is typically surrounded by a thin mantle, which encloses the mantle cavity in which the gills
are found, and secretes the shell material in shelled molluscs.
Gastropoda
Gastropod literally means ‘stomach-foot’ and they are the most successful and most commonly
seen class of molluscs. Gastropods have a single, often coiled, shell within which the body is
protected. All gastropods have a toothed radula – a chitinous band in the mouth covered in
horny teeth used to scrape and rasp food. The majority of gastropods feed on algae, sponges,
other molluscs and small invertebrates. This class includes conchs (Figure 5.4), cowries, helmet
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shells, whelks, olive and cones shells. It is important to note that the mantle can extend over
the entire shell in some species making gastropods harder to identify.
Figure 5.4 Queen conch
Flamingo tongue
The flamingo tongue (Figure 5.5) is a type of cowrie. They live on gorgonians feeding on the
polyps. The Caribbean spiny Lobster is a major predator of flamingo tongues. Overexploitation
of lobsters has been linked to increases in flamingo tongue populations. As flamingo tongues
are more conspicuous than lobsters, they are monitored as a potential indicator species for
lobster population status.
Figure 5.5 Flamingo tongue
Phylum Echinodermata (Sea Urchins and Sea Cucumbers)
The Echinoderms constitute around 7000 described living species with another 13,000 known
from fossil records dating back 600 million years ago. The name echinoderm literally means
‘spiny-skinned’ and refers to their endoskeleton of calcium carbonate plates usually baring
spines, which characterises this phylum. Also characterising this phylum is five-part radial
symmetry and an internal water vascular system. This water vascular system is composed of an
intake sieve plate in which water is drawn into a series of canals which radiate through the
body and end in tube feet. Echinoderms have no excretory organs but usually a complete gut
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(mouth, stomach, intestines and anus) in one. The families are exclusively marine and the
majority of species have separate sexes. The echinoderms are also renowned for their ability to
regenerate lost body parts.
Echinoidea (Sea Urchins)
Sea Urchins (Figure 5.6) are commonly seen on the reefs and are normally round-bodied with
stiff and often sharp spines. Most species are nocturnal and are seen in caves and crevices
during the day. They are major grazers on the reef helping to turnover reef sediments and
helping to release valuable nutrients. Sea urchins graze on algae and other organisms found on
the substrate such as sponges and bryozoans.
Figure 5.6 Sea urchin
The species Diadema antillarum, commonly known as the long-spined sea urchin (Figure 5.7), is
monitored in Bacalar Chico Marine Reserve. Once forming dense aggregations in areas with an
abundance of algae, Diadema populations were almost wiped out in the 1980s throughout the
Caribbean due to a disease outbreak. The juvenile Diadema has black and white banded spines,
whilst the adult has plain black or white spines.
Figure 5.7 Diadema/Long-spined sea urchin, Diadema antillarum
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Holothuroidea (Sea Cucumbers)
Sea cucumbers (Figure 5.8) are elongate animals with a mouth surrounded by short tentacles at
the anterior end of the body. They are normally seen lying on the sand floor where they feed by
ingesting large amounts of sand and digesting the organic material. Sea cucumbers often leave
a trail of sand as they feed as sand is excreted from the anus. The majority of sea cucumbers
are large, solid, cylindrical-shaped animals, with some species having long, branching tentacles
surrounding their mouths. As a defense mechanism some species are able to eject cuvierian
tubules (sticky, white tubules) if disturbed while others can eviscerate (expel internal organs by
rupturing the body wall). However they are able to regenerate lost body organs in time.
Figure 5.8 Sea cucumber
Phylum Chordata (Tunicates)
The tunicates or ascidians, form part of the Urochordata, a subphylum of the Chordata. The
Phylum Chordata includes the invertebrate tunicates, fish, reptiles, birds and mammals.
Although the ascidians are invertebrates they are included in the Chordates because their
larvae have a notochord (which develops into a backbone in the vertebrates), which is lost in
the adults. Therefore tunicates are the invertebrates most closely related to humans. All
ascidians are hermaphrodites and can reproduce asexually by budding or sexually. The larvae of
tunicates resemble a tadpole, and once the larvae have settled on the substrate it loses its tail
and develops into a fixed ascidian.
Tunicates are sessile filter feeders; water is drawn into an inhalant siphon and then expelled
through a separate exhalent siphon. The gill slits, or stigmata, of the bronchial sac are covered
in beating hair- like cilia and generate the water movement through the animal. Organic matter
in the water is retained within the tunicate by a layer of mucus lining the bronchial sac.
Ascidians are fierce competitors for space on the reef, and can rapidly overgrow corals, sponges
and bivalve molluscs. The main predators of ascidians include starfish, polychaete worms,
various fish species and flatworms. Some commensals and parasites of tunicates include
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shrimps, copepods, amphipods, molluscs, and protozoans. Tunicates are embedded in a
gelatinous-looking ‘tunic’ and can occur as solitary or colonial individuals.
Solitary tunicate
Solitary tunicates (Figure 5.9) can form pelagic or sedentary forms. They are usually less than 20
cm in size. They come in many different colours and forms, but all can be identified by the two
siphons. Solitary species are often covered in dense assemblages of sponges, other tunicates
and algae.
Figure 5.9 Solitary tunicate
Colonial/encrusting tunicate
Colonial tunicates (Figure 5.10) can comprise of large numbers of individual tunicates or may
form an encrusting mat (Figure 5.11) with openings dotted over the surface of a continuous
tunic. Tunicates are often mistaken for sponges but can be distinguished as, unlike sponges, the
pores will react and close when wafted. They are found encrusting over the reef. Encrusting
tunicates compete with hard corals, and can overgrow them completely.
Figure 5.10 Colonial tunicate
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Figure 5.11 Encrusting mat tunicate
Lobsters
Caribbean Spiny Lobster (Panulirus argus)
The Caribbean spiny lobster (Figure 5.12) is the most commonly seen lobster on the reef. It is
easily identified by the sharp spines covering the head and antennae. The carapace is brown
with dark spots, whilst the abdomen is brown with light spots. The juvenile has a dark brown
body with purple markings, brown and white bands on the legs and a white band on the tail.
Figure 5.12 Caribbean spiny lobster, Panulirus argus
Spotted spiny lobster (Panulirus guttatus)
The spotted spiny lobster (Figure 5.13) has a brownish, purple body which is covered in bright
white spots, distinguishing it from the Caribbean spiny lobster. The last segment of the legs has
brown stripes. Smaller than the Caribbean spiny lobster, they are not as commonly seen.
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Figure 5.13 Spotted spiny lobster, Panulirus guttatus
Spanish lobster (Scyllarides aequinoctialis)
The Spanish lobster (Figure 5.14) is a type of slipper lobster. Very uncommon in Bacalar Chico
Marine Reserve, the Spanish lobster doesn’t look like any other lobster, with a wide body and
heavy armour. Four to five purple spots are located on the first segment of the abdomen. The
body is reddish to orange brown, whilst the legs are yellow with small brown spots.
Figure 5.14 Spanish lobster, Scyllarides aequinoctialis
Phylum Cnidaria (Corals, Anemones, Hydroids, and Jellyfish)
The Cnidaria are a large and diverse phylum which include hard and soft corals, anemones and
jellyfish. There are more than 10,000 described species of Cnidaria and they form the basis of
many tropical and colder water marine ecosystems. This diverse group is united by the fact that
all members are armed with stinging cells called nematocysts and the name Cnidaria comes
from the Greek meaning ‘stinging creature’. The nematocysts (Figure 5.15) are barbed,
harpoon-like darts tipped with poison that are discharged on contact with prey or predators.
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Figure 5.15 Diagram of a nematocyst
Cnidarians are radially symmetrical (the body is symmetrical around a central axis). Cnidarians
can have one of two basic body plans, a polyp, with the tentacles and mouth facing down, or a
medusa, with the tentacles and mouth facing. Some Cnidarians may pass through both life
forms during their life cycle, whilst others only pass through one of the two. Some Cnidarian
species consist of a single polyp, such as sea anemones and mushroom corals, whilst other
species comprise colonies of polyps, such as most hard and soft corals. The basic body plan of
the polyp is a cylindrical column with a ring of tentacles surrounding the only opening. The main
column of the body consists of an outer layer, the epidermis, a middle layer, the mesoglea and
an inner layer, the gastrodermis. There are no respiratory, circulatory or excretory organs and
only a hydrostatic (water based) skeleton.
Cnidarians not only rely on their stinging cells to catch prey but also use suspension feeding to
capture food. Many cnidarian species also harbour symbiotic single-celled algae, called
zooxanthellae, which contribute nutrients to the cnidarian. In some hard coral species it is
estimated that the algae can contribute up to 80% of the daily food requirements of the coral.
There are four important classes of this Phylum.
Scyphozoa (True Jellyfish)
The Scyphozoa consist of over 200 species of pelagic, free-swimming organisms that can range
in size from twelve millimetres to more than two meters across. Their life cycle involves an
alternation between sessile polyp phase and a free-swimming medusa stage. The Scyphozoa
have only one opening, like all cnidarians, through which food and waste must be passed out.
Surrounding the ‘mouth’ are usually four oral arms or tentacles which contain the stinging cells
that are used for paralyzing prey and defence. The larger jellyfish prey on fish and invertebrates
whilst smaller jellyfish may feed on suspended organic particles in the water. One genus of the
jellyfish family, Cassiopeia spp. (Figure 5.16) has evolved an unusual feeding style. It lies upside
down on the seafloor in the shallows so that its tentacles face towards the surface. The body
tissue of the jellyfish contains photosynthetic dinoflagellates, which manufacture their own
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food and provide food for the jellyfish. Cassiopeia spp. are seen abundantly throughout the
seagrass beds and mangroves in Bacalar Chico Marine Reserve.
Figure 5.16 Cassiopeia spp. (from seaslugforum.net)
Anthozoa (Gorgonians, Corals, Anemones)
The Anthozoa is the largest of the Cnidarian classes, with over 6000 described species. They are
exclusively marine, sedentary and can occur as individual polyps or in colonies. They have no
medusoid stage in their life cycle.
Subclass Octocorallia:
The polyps have eight internal walls, and therefore have eight-fold radial symmetry, and
feathered tentacles. Most octocorals produce spicules within their body tissue to provide
support. The majority of octocorals are filter feeders and may also house symbiotic
zooxanthellae.
The order Gorgonacea, sea fans, sea rods, sea plumes (Figure 5.17) and encrusting gorgonians
(Figure 5.18), are typically brightly coloured and form fan or branched shapes that align
themselves perpendicular to the prevailing current. They are tougher than other members of
the octocorals and have a firm internal skeleton composed of a proteinaceous material called
gorgonin.
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Figure 5.17 Gorgonians (from left to right) sea rod, sea fan and sea plume
Figure 5.18 Encrusting gorgonian
Subclass Hexacorallia (Anemones and Hard Corals):
The Hexacorallia is a diverse group and hexacoral polyps can vary greatly in form. They have six
tentacles and internal walls, or a multiple thereof, and can have as few as 6 or as many as
several hundred tentacles. The size of polyps range from less than 1 mm to greater than 1 m in
diameter, and may be solitary or colonial.
The order Actinaria (sea anemones) (Figure 5.19) normally form distinctive solitary polyps, with
an upwards facing mouth and a flattened “foot” for attachment. Their tentacles contain the
stinging nematocysts and anemones are host to many animal symbionts taking advantage of
this extra protection. Anemones are host to copepods, shrimp and half crabs, which are
adapted to use them for shelter.
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5
Figure 5.19 Anemone
The order Zoanthidea (zoanthids) (Figure 5.20) are mainly colonial. They have relatively small
polyps with a double row of short tentacles that arise around the edge of the polyp. Many
species are able to incorporate sand into their mesoglea4 for support. Zoanthids can reproduce
asexually to form colonies or clonal 6aggregates, or through free spawning. Zoanthids will close
when disturbed.
Figure 5.20 Colonial zoanthid
The order Coralliomorpharia (corallimorphs) (Figure 5.21) are similar in appearance to
anemones. Most reef species harbour zooxanthellae. They can be found as solitary individuals
or in small to large colonies. Corallimorphs form a flat disc with stubby tentacles radiating from
the mouth. Unlike anemones, the mouth is protruding.
5
Mesoglea is the translucent, inert, jelly-like substance that makes up most of the sea
creatures in the phyla Cnidaria.
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Figure 5.21 Corallimorph
Members of the order Scleractinia (hard or stony corals) are the most important reef-building
animals, and there are over 2500 species worldwide. Although some species of hard coral can
be easily identified there are several genera in which individual species can only be identified
after examination of the skeleton under a microscope. This is partly because the morphology of
coral colonies can alter depending on the environmental and biological conditions they are
growing in. It is important to recognise the coral growth forms in order to describe the
topography and heterogeneity of the coral reef (Table 1).
Hydrozoa (Hydrozoans)
The Hydrozoa are a diverse group of organisms with about 2700 species. Most hydrozoans
(Figure 5.22) are colonial and can form a variety of life forms from small, feather-like branched
colonies, to large colonies with a calcareous skeleton. Most hydrozoans alternate between a
polyp and a medusa stage, when they can be difficult to distinguish from a true jellyfish.
Individual polyps often have specialised functions, such as for feeding or for reproduction.
Millepora spp. (Fire Coral)
Millepora spp. are characterised by the hair-like stinging cells which will give nasty sting if
accidentally touched. Two species are found in Bacalar Chico Marine Reserve; Millepora
alcicornis (branching fire coral) and Millepora complanata (blade fire coral). Millepora alcicornis
(Figure 5.23) often encrusts around sea rods and other gorgonians. Branching fire coral can be
identified by the encrusting base and fine hairs present on a smooth surface. When the
nematocysts retract the surface appears covered with tiny pores.
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Figure 5.23 Millepora alcicornis (branching fire coral)
Blade fire coral (Figure 5.24) grows in flat protrusions from an encrusting base. As with
branching fire coral, the colour varies from tan to mustard brown, with tips appearing bleached
and pale.
Figure 5.24 Millepora complanata (blade fire coral)
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CHAPTER X: ORDER SCLERACTINIA: INTRODUCTION AND
IDENTIFICATION
Coral reefs are composed of massive deposits of calcium carbonate, the majority of which is
produced by the hard corals. Hard corals form the Order Scleractinia, part of the anthozoans, a
class of animals that belong to the phylum Cnidaria. They are characterised by radial symmetry
and specialised stinging cells called nematocysts. Corals are normally formed from colonies of
polyps and are closely related to the sea anemones. shows the structure of a polyp. The hard
corals secrete calcium carbonate around the body of the polyp which provides an external
skeleton to house the polyps. The polyps sit in tiny cavities in the calcium carbonate skeleton,
known as corallites, and can vary in size from a few millimetres to several centimetres.
The living part of the coral is only found as a thin veneer which covers the old coral skeleton
which acts as the foundation from which the coral grows. The foundation of the reef may also
be composed of other calcium carbonate deposits, including shells, hard parts of crustaceans
and the green algae species which secrete calcium carbonate.
Figure 6.1 Polyp and medusa forms of cnidaria.
The polyps are typically carnivorous and coral polyps consist of a ring of tentacles surrounding a
mouth into which the food captured by the nematocysts is passed. The nematocysts also act as
the corals defence and the tentacles also clear debris away from the mouth (Figure 6.2).
Figure 6.2 The ring of tentacles surrounding the central mouth of a coral polyp
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Although hard corals are found in warm and cold waters, it is only in the tropics that coral reefs
develop. This is because there are two groups of corals, the hermatypic and ahermatypic corals.
The main difference between the groups of corals is that most hermatypic corals contain
symbiotic algae. The hermatypic corals are the reef-building corals and are found exclusively in
warm, subtropical waters. Figure 6.3 shows the structure of the skeleton of a hard coral. The
walls or ridges that radiate from the centre of the corallite are known as septa and are clearly
visible in Figure 6.3. It is often this skeletal detail that must be examined closely under a
microscope to identify several species of hard coral. The polyps of most hard corals are not
visible during the day and are drawn into the skeleton. For the purpose of Blue Ventures
surveying method, volunteers should learn the scientific names of all coral species.
Figure 6.3 Cross section through skeleton of a hard coral showing the structure of a
corallite.
Acroporidae
The Acroporidae family (Figure 6.4) of scleractinian corals all have distinct hooded corallites.
1. Staghorn: Acropora cervicornis
2. Elkhorn: Acropora palmata
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Figure 6.4 Acropora cervicornis
6.2. Poritidae
The Poritidae (Figure 6.5) all have very small, pore-like corallites. The corallites also share walls.
1. Mustard Hill: Porites astreoides
2. Finger: Porites porites
Figure 6.5 Porites astreoides
6.3. Siderastreidae
The Siderastreidae (Figure 6.6) display “innie” corallites with protruding septa. This gives this
family of corals a pitted appearance.
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Massive Starlet: Siderastraea siderea
Lesser Starlet: Siderastraea radians Figure 6.6 Siderastraea siderea
6.4. Agariciidae
The Agariciidae (Figure 6.7) is one of the larger families of corals. As the common names
suggest, species in this family have the appearance of a cross section of a lettuce.
Lettuce: Agaricia agaricites
Thin Leaf Lettuce: Agaricia tenuifolia
Low Relief Lettuce: Agaricia humilis
Fragile Saucer: Agaricia fragilis
Whitestar Sheet: Agaricia lamarcki
Sunray Lettuce: Helioseris cucullata
Figure 6.7 Agaricia agaricites
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6.5. Astrocoeniidae
The Astrocoeniidae (Figure 6.8) can be identified by their small “outie” star-like corallites.
1. 10-Ray Star: Madracis decactis
2. 8-Ray Finger: Madracis formosa
3. Yellow Pencil: Madracis
auretenra
4. Blushing Star: Stephanocoenia intersepta
Figure 6.8 Stephanocia intersepta
The
Figure 6.9) is a very large and variable family, including some brain corals and the
Montastrea star coral complex.
Symmetrical Brain: Diploria strigosa
Knobby Brain: Diploria clivosa
Grooved Brain: Diploria labyrinthiformis
Boulder Brain: Colpophyllia natans
Great Star: Montastrea cavernosa
Lobed Star: Montastrea annularis
Mountainous Star: Montastrea faveolata
Boulder Star: Montastrea franksi
Golfball: Favia fragum
6.6. Faviidae
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Figure 6.9 Diploria strigosa
6.7. Meandrinidae
All corals in the Meandrinidae family (Figure 6.10) have highly protruding septa.
Elliptical Star: Dichocoenia stokesi
Maze: Meandrina meandrites
Pillar: Dendrogyra cylindrus
Smooth Flower: Eusmilia fastigiata
Figure 6.10 Dichocoenia stokesi
6.8. Caryophylliidae
The Caryophylliidae (Figure 6.11) resemble flowers, with the polyps located on long stalks 1.
Smooth Flower: Eusmilia fastigiata
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Figure 6.11 Eusmilia fastigiata
6.9. Mussidae
All members of the Mussidae family (Figure 6.12) have a distinct fleshy appearance.
3.
4.
5.
6.
7.
8.
9.
Sinuous cactus: Isophyllia sinuosa
Rough star: Isophyllastrea rigida
Ridged cactus: Mycetophyllia lamarckiana
Knobby cactus: Mycetophyllia aliciae
Rough cactus: Mycetophyllia ferox
Spiny flower: Mussa angulosa
Artichoke: Scolymia spp.
Figure 6.12 Isophyllastrea rigida
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