A macroecological study of Caribbean parrotfishes

Abstract

Parrotfishes contribute to more than 80% of the biomass of herbivorous fishes in the Caribbean and they have been the dominant grazers on reefs since 1983. Maintaining healthy parrotfish populations is essential to help conserve benthic habitat cover which is suitable for the settlement and growth of reef building corals. However, the key environmental factors that currently affect local parrotfish abundance and population structure are scarcely known. Many reef studies are constrained to a limited geographical scale which may not be applicable at larger spatial scales. Parrotfish data across the wider Caribbean will help to overcome such issues. This study investigates three relationships including parrotfish density and benthic habitat variables (Chapter 2); parrotfish density and fishing pressure (fisher density, human population, MPA protection) (Chapter 3); and parrotfish size at sex change and fishing pressure (Chapter 4). Fish and benthic habitat surveys at 7 to 15 sites were conducted in each of eight Caribbean countries including Antigua, Bonaire, Barbados, Curaçao, Dominican Republic, Jamaica, St. Lucia, and St. Vincent and the Grenadines. Parrotfish abundance was positively correlated with coral cover and negatively correlated with macroalgal cover. Parrotfish abundance had a significant correlation with reef complexity (Chapter 2). Different sizes of parrotfish were associated with different habitats (Chapter 2). Fishing is likely to have reduced fish numerical abundance and biomass even at Caribbean scale (Chapter 3). While parrotfish biomass was significantly higher within MPAs, parrotfish numerical density was not significantly different (Chapter 3). The density of terminal parrotfish was significantly different (Chapter 4). Furthermore, fishing pressure was significantly correlated with the size at which phase change between initial and terminal phases occurs (Chapter 4). This research demonstrates the major drivers of Caribbean parrotfish abundance and biomass which may help inform management of parrotfish and promote further coral reef ecosystem recovery.