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Atlantic and Gulf Rapid
Reef Assessment
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Coral reefs
| Coral ID | Algae | Fishes
Coral reef fishes
The complex structure of coral reefs offer fish numerous shelters, refuges
and microhabitats. Fish assemblages vary greatly among habitat patches at all
spatial scales (Williams 1991) and often show a high degree of site attachment
(Sale 1978b). Due to the high
diversity of coral reef-associated fishes, numerous interactions occur and
complex trophic structures are formed including non-territorial herbivores, territorial
herbivores, planktivores, corallivores, spongivores/octocorallivores,
invertebrate or bottom feeders, sedentary predators, and free swimming
predators. The AGRRA protocol surveys fish that play an important role in reef
ecology (e.g., herbivore, carnivore), are important commercial fish species,
and/or are likely to be affected by human impacts. Scarids and acanthurids are
the most important macroherbivores on the reef, although pomacentrids are also
important. Important corallivores include butterflyfish and angelfish and are
susceptible to removal for the aquarium trade. Groupers and snappers are
important predatory fish and are some of the most significant commercial
finfish. Other predatory fish include bar jacks and barracudas. Other commercially
significant species include hogfish, spanish hogfish, triggerfish and grunt.
Fish community structure is regulated by numerous biotic processes including
competition, predation, and recruitment limitation. Resource limitations may
cause significant competition among fishes and ultimately can determine the
abundance, distribution and diversity of fish populations as fishes compete for
resources (Ross 1986). Predation is another important factor structuring fish
assemblages. Specific morphological and behavioral adaptations are evidence of
predators developing efficient capture techniques as well prey developing
effective defense mechanisms in response to predation (Hixon 1991). Predation
contributes to structuring fish communities, sometimes revealing a negative
relationship between predator and prey-fish densities. The survivorship of
juveniles is quite low due to high levels of predation on newly recruited fish
(Sale and Ferrell 1988). Most reef fishes have planktonic larval stages and are
subject to high mortality and low recruitment. Patterns of adult abundance are
therefore affected by the availability of larvae and survival of juveniles (Sale
1988). Reefs can act as sources or sinks of larvae over various spatial scales.
Fish populations are influenced by the source of larvae and can be larval
limited, particularly if the larval source is located upstream from a fish
population (Cowen 1985).
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Fish
identification
In addition to the 2m wide belt transects used to assess
the abundance and size of fish, AGRRA has collaborated with the Reef
Environmental Education Foundation (REEF - www.reef.org).
REEF formed a non-profit organization in 1990 with the mission to educate,
enlist and enable divers and non-divers alike to become active stewards in the
conservation of coral reefs and other marine habitats. The founders of REEF,
Paul Humann and Ned DeLoach, have published several fish identification guides
(books, cd-roms, slides) to aid in the identification of fish in the Caribbean.
Although using scientific names for identifying fish is preferred, especially
since one fish can have more than one common name, the American Fisheries
Society has published a list of preferred common names, which the
Humann/DeLoach field guides have adopted. These educational materials are used
as part of the AGRRA training workshops.
Distinctive features such as anatomy, colors, and markings
are used to distinguish between the more than 500 coral reef fish species found
throughout the Caribbean (Humann 1994). The anatomical
features used to identify individual fish speciesinclude fins, spines, eyes,
mouth, and gills. Colors of fish vary considerably among species and even
within a single individual (e.g., light silver to dark gray). Several fish are
capable of changing, lightening or darkening their colors (e.g., groupers).
Distinctive markings are used to identify fish including bars (vertical marks),
stripes (horizontal marks) and bands (diagonal marks). The following diagrrams
illustrate some of these distinctive features. The illustrations for marking
and twelve categories for body forms are based on Humann (1994).
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Coral reefs | Coral ID | Algae | Fishes
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