TITLE:
Have the Algae-Grazing Fish in the Back Reefs of Jamaica and Grand Cayman Changed in Size? A View across 36 Years
AUTHORS:
Matthew J. Draud, M. Itzkowitz
KEYWORDS:
Caribbean, Scaridae, Acanthuridae, Fishing Intensity, Body Shape
JOURNAL NAME:
Open Journal of Marine Science,
Vol.8 No.2,
April
30,
2018
ABSTRACT: The island of Jamaica is often cited as an example of how overfishing has
dramatically reduced the sizes of coral reef fishes. To examine the change in
fish sizes over a 36-year period, we analyzed data from systematic surveys
conducted in 1977 and 2013/14 of the sizes and relative abundances of four
common algae-grazing fishes in the shallow backreef habitats of Jamaica and
Grand Cayman. The four species are: striped parrotfish (Scarus iseri), stoplight
parrotfish (Sparisoma viride), ocean surgeon (Acanthurus tractus) and
the blue tang (Acanthurus coeruleus). We predicted that all four species
would be larger in Grand Cayman than in Jamaica in 1977 as well as in
2013/14, because Grand Cayman has been cited as having less fishing pressure
than Jamaica. For the same reason, we expected all four species would have
declined in size over the 36 years in Jamaica but not in Grand Cayman. Furthermore,
we predicted that the compressed body shape of the ocean surgeon
and the blue tang would have made them especially vulnerable to net and trap
fishing compared to the two parrotfishes, and that accordingly the effects of
overfishing would be greater in these two species. We rejected this hypothesis.
The size distributions of the laterally compressed species changed significantly
on both islands over the 36-year time span, although not as predicted. At both
islands, the blue tangs shifted toward smaller sizes and the ocean surgeons
shifted toward larger sizes. There were no size distribution changes detected
in the two fusiform species. There was also no support for the prediction that
the sizes of these four species were larger in Grand Cayman than in Jamaica
during either time period.