Have the Algae-Grazing Fish in the Back Reefs of Jamaica and Grand Cayman Changed in Size? A View across 36 Years

Matthew J Draud,M Itzkowitz

doi:10.4236/ojms.2018.82016

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.

Highlights

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 the effects of overfishing would be greater in these two species
By the early 1990s, it was generally accepted that the coral reef fish community in Jamaica was in decline and among the most intensely fished in the Caribbean (Allison, 1992 [1]; Hughes, 1994 [2]; Sanderman & Woodley, 1994 [3]; Sary, 1995 [4]; Hardt, 2009 [5]), with fishing pressure in Jamaica being estimated at more than twice the estimates of the highest islands (Hawkins & Roberts, 2004 [6])
Hawkins & Roberts (2004 [6]) and others have argued that the intense “artisanal fishing” was responsible for the relatively smaller fish sizes in Jamaica compared to other Caribbean Islands

Summary

Introduction

By the early 1990s, it was generally accepted that the coral reef fish community in Jamaica was in decline and among the most intensely fished in the Caribbean (Allison, 1992 [1]; Hughes, 1994 [2]; Sanderman & Woodley, 1994 [3]; Sary, 1995 [4]; Hardt, 2009 [5]), with fishing pressure in Jamaica being estimated at more than twice the estimates of the highest islands (Hawkins & Roberts, 2004 [6]). Munro (1983 [7]) and Sary et al (2003 [9]) warned that without a more intense management of the artisanal fisheries, the Jamaican reef fish populations would continue to decline both in numbers and sizes. Aronson & Precht (2006 [14]) argue that climate change and marine diseases are more potent factors in large-scale coral reef degradation

Methods

Results

Conclusion