Caribbean parrotfish foraging: An interspecific comparison of algal preferences

In recent decades, reduced grazing pressure caused by a die-off of Diadema antillarum and the overexploitation of herbivorous fishes have facilitated a phase shift from coral to algal dominated reefs. Thus, conservation of herbivorous fishes has become increasingly important on coral reefs. In the Caribbean reefs, parrotfish are the dominant herbivores. Studies have been conducted on parrotfish grazing, but there is a lack of knowledge about specific algal preferences. This study examined differences in bite frequencies on algal types and algal preferences of the most common parrotfish species of Bonaire, Dutch Caribbean. Mean bite frequencies (bites 30 min-1 ) and preferences were determined by offering algal plates with Padina sp., Ulva sp., Sargassum sp., and turf algae to parrotfish on the coral reef flat. During field observations, data was collected on the number of bites taken and algal type grazed by each individual parrotfish. Parrotfish as a group, and individual species (Sparisoma rubripinne, Scarus viride, and Sparisoma aurofrenatum), demonstrated significant differences in mean bite frequencies on algal types offered. There were also significant differences in mean bite frequencies among the three parrotfish species. All species of parrotfish, collectively and individually, demonstrated preferences for Padina sp. and avoidances for all other algal types offered. Determining which algal types parrotfish graze, and how grazing differs among parrotfish species is ecologically important. The results provide an understanding of how the selective pressures of specific herbivores may help regulate harmful macroalgae, and suggest the importance of maintaining the diversity of herbivorous fishes on the reef.

This student research was retrieved from Physis: Journal of Marine Science XIV (Fall 2013)19: 110-117 from CIEE Bonaire.