Effects of a predatory fish on the recruitment and abundance of Caribbean coral reef fishes

Abstract

The importance of postrecru~tment factors in determining assemblage structure of coral reef f~shes is one of the most controversial toplcs In community ecology. To document the effects of predat~on on postlarval recruitment and the abundance of resident reef flshes, I manlpulateti small plscivorous fish on 12 model patch reefs located in uniform seagrass habitat in the U S. Virgln Islands. SIX reefs served as controls and 6 were used for predator removals. Weekly censuses were conducted for 2 mo before and after predator manlpulatlons to document effects of removals. Remo\.dls of the squ~l-relfish Holocentrus ddscens~onls had a signlflcant effect on the recruitment and abundance of othelspecles. During the first renloval expenment, which was conducted during a peak recruitment perlod, hlgh densities of squirrelfish depressed postlar\.dl recruitment and juvenile dhundance of grunts Haemulon spp.. the most abundant species on the reefs. Following peak recruitmc.nt of grunts, a second squirrelf~sh removal resulted in increases in juvenile grunt abundance on predator-removal reefs. These results indlcate the importance of postrecruitment factors, particularly predation, in structuring assemblages of coral reef fishes at a small spatial scale.