Interspecific differences in foraging behaviour and functional role of Caribbean parrotfish

Abstract

Herbivory is one of the most important biological processes influencing coral reefs. In the highly diverse Indo-Pacific reef fish communities, different herbivores can have strikingly different functions. We investigated the extent of functional diversity among herbivorous parrotfish of the more species-depauperate Caribbean Sea. We carried out observations of seven species of parrotfish (Scarus taeniopterus, Sc. vetula, Sc. iserti, Sparisoma viride, Sp. aurofrenatum, Sp. rubripinne and Sp. chrysopterum) on four Barbadian coral reefs to collect information on foraging techniques, rates, and targets, and found marked interspecific variation. Species of the genus Scarus had higher foraging rates than those of the genus Sparisoma. Different species took varying amounts of live coral, turf algae and macroalgae. A functional categorization based first on foraging technique (contact or no contact with the substratum) and secondarily on the more conventional criterion of foraging target (macroalgae, turf algae and live coral) allowed us to classify Sc. taeniopterus and Sc. iserti as ‘scrapers’, Sp. aurofrenatum, Sp. rubripinne and Sp. chrysopterum as ‘grazers’, Sp. viride as a ‘bioeroder’ and Sc. vetula as a ‘bioeroder/scraper’. This functional group affiliation, together with species-specific foraging rates, allows us to predict the role of Caribbean parrotfish on major coral reef processes and their impact on coral reef benthic communities.