Short-term changes in the structure of a fish community following coral bleaching at Ishigaki Island, Japan

Abstract

Short-term changes in a fish and coral community on an outer reef at Ishigaki Island, Ryukyus Islands of Japan, were quantified and related to severe coral bleaching that occurred in the summer of 1998. Prior to July 1998, the benthic substrata along the transect consisted mostly of living Acropora spp. By late September 1998, however, most of the living coral had died and the dead coral skeletons were coated with filamentous algae by late October 1998. In the fish community, both the number of individuals and species per transect did not change one month after the coral bleaching, however, species diversity decreased. Although the number of individual omnivores and carnivores did not differ before and after the coral bleaching, the number of coral-polyp feeders decreased. In contrast, the number of herbivores, particularly two species of acanthurids, increased one month after the coral bleaching. Differences in abundances of hervivores and coral-polyp feeders after the coral bleaching appear to be related to changes in the benthic habitat. These results suggest that the two acanthurid fish species responded to the increase in algal biomass by migrating from adjacent habitats to the outer reef.