HABITAT CHARACTERISTICS AFFECTING FISH ASSEMBLAGES ON A HAWAIIAN CORAL-REEF

Habitat characteristics of a reef were examined as potential influence s on fish assemblage structure, using underwater visual census to esti mate numbers and biomass of all fishes visible on 42 benthic transects and making quantitative measurements of 13 variables of the correspon ding physical habitat and sessile biota. Fish assemblages in the diver se set of benthic habitats were grouped by detrended correspondence an alysis, and associated with six major habitat types. Statistical diffe rences were shown between a number of these habitat types for various ensemble variables of the fish assemblages. Overall, both for complete assemblages and for component major trophic and mobility guilds, thes e variables tended to have higher values where reef substratum was mor e structurally or topographically complex, and closer to reef edges. W hen study sites were separately divided into five depth strata, the de eper strata tended to have statistically higher values of ensemble var iables for the fish assemblages. Patterns with depth varied among the various trophic and mobility guilds. Multiple linear regression models indicated that for the complete assemblages and for most trophic and mobility guilds, a large part of the variability for most ensemble var iables was explained by measures of holes in the substratum, with impo rtant contributions from measured substratum rugosity and depth. A str ong linear relationship found by regression of mean fish length on mea n volume of holes in the reef surface emphasized the importance of she lter for fish assemblages. Results of this study may have practical ap plications in designing reserve areas as well as theoretical value in helping to explain the organization of reef fish assemblages. (C) 1998 Elsevier Science B.V.