EFFECTS OF EXPERIMENTAL CORAL DISTURBANCE ON THE STRUCTURE OF FISH COMMUNITIES ON LARGE PATCH REEFS

Communities of reef fishes on 10 large isolated patch reefs or 'bommie s' (108 to 267 m(2)) were monitored at 1 to 2 mo intervals over 1 yr, and then the hard corals on 5 of the bommies were physically disturbed by breaking the colonies into small pieces with a mallet. Monitoring continued for a further year after the disturbance. Coral cover at the impacted bommies decreased from similar to 66 to similar to 29 % by t he end of the study, while coral cover had increased by 5 % in the sam e period at the control bommies. There were significant declines in sp ecies richness and total abundance of fishes on the impacted bommies, but multivariate analyses showed that the disturbance had no significa nt effect on spatiotemporal patterns of adult relative abundance and l arval recruitment at the community level. Effects of disturbance on th e abundance and species richness of 6 families and 8 distinct ecologic al categories of fishes were also examined. There were significant dec lines in the abundance of 1 family (the Chaetodontidae) and 1 ecologic al category (water column/substratum feeding Pomacentridae), and signi ficant declines in the species richness of 2 families (the Apogonidae and Scaridae) and 1 ecological category (invertebrate feeders). Althou gh coral disturbance did effect some elements of the fish communities, it appears that patterns of spatial heterogeneity in the underlying h ard substrata at each bommie were also important determinants of fish community structure. Hence, historical patterns of coral growth and su bstrate consolidation, together with the contemporary coral community, can affect the structure of fish communities on these large patch ree fs. Further studies of fish-habitat associations, together with field experiments which manipulate both the underlying substratum and the ab undance of live corals, will be necessary to determine the relative im portance of each of these habitat characteristics to reef fishes.