TITLE:
Comparisons of Group-Size, Composition and Movement of Herbivorous Reef Fish in Jamaica and Grand Cayman Island
AUTHORS:
Layla Al-Shaer, Andrew Bloch, Matthew Draud, Brandon Baumann, Murray Itzkowitz
KEYWORDS:
Coral Decline, Foraging Behavior, Algae-Grazing, Herbivore, Scaridae, Acanthuridae
JOURNAL NAME:
Open Journal of Marine Science,
Vol.10 No.1,
December
13,
2019
ABSTRACT: The
decline in herbivorous fishes is an important contributing factor to the
degradation of coral reefs, because their reduction contributes to macro algae
overgrowth, which can have harmful effects on corals. Herbivorous fish often
form mixed-species groups to locate foraging sites and for defense. The
movements and compositions of these groups are dependent on the relative numbers
of different species present. Some species, such as the striped parrotfish (Scarus iserti) and ocean surgeonfish (Acanthurus bahianus), serve as core
species that lead mixed-species groups. Others, such as the redband (Sparisoma aurofrenatum) and stoplight
parrotfishes (Sparisoma viride), follow
core species as their associates. Despite the potential importance and abundance
of mixed-species groups on reefs, little attention has been given to their
composition and movements. Our intent was to determine whether the social
dynamics of mixed-species groups in Jamaica were similar to those of Grand
Cayman. The overall sizes of mixed-species groups were smaller in Grand Cayman.
Focal striped parrotfish in Grand Cayman formed smaller groups, changed
composition less, and moved less frequently than in Jamaica. Although probably
more abundant than striped parrotfish, the ocean surgeonfish in Grand Cayman
did not function as a core species but rather attached themselves as associates
to the smaller striped parrotfish groups. Redband parrotfish moved less often
in Grand Cayman, and appeared to be more dependent on striped parrotfish groups
than stoplight parrotfish. While previous studies on herbivorous reef fish have
shown that changes in foraging patterns can change with location, perhaps
related to structural heterogeneity and resource distribution, this study
illustrates that social interactions between common members of mixed-species
groups also change. We suggest that the intra and interspecific social
interactions in Grand Cayman are less attuned to finding erratically located
high quality resources than those in Jamaica. Other plausible explanations are
also considered.