SPATIAL-DISTRIBUTION OF CHAETODONTIDAE IN DIFFERENT CORAL-REEF SECTORS OF MOOREA-ISLAND IN FRENCH-POLYNESIA

Species composition (presence-absence and abundance) of chaetodontid f ish assemblages has been investigated at four sites on Moorea Island ( French Polynesia), in order to understand the spatial distribution of the butterflyfishes and to establish their relations with some benthic groups. Four fish assemblages were identified, each one typical of a particular geomorphological entity of the reef: (1) the fringing reef of the lagoon and the reef flat of the fringing reef of bays, (2) the barrier reef and the reef crest of the fringing reef of bays, (3) the reef wall of the fringing reef of bays, and (4) the outer slope (coast al oceanic assemblage). Chaetodontid fish assemblages of bays are inte rmediate between the assemblages of the lagoon and of the ocean. Among the five macrobenthic groups considered (corals, algae, molluscs, ech inoderms, sponges), corals seem to be the most important factor affect ing the spatial distribution of butterflyfishes. The other groups are also of some importance; this result is related to the diet of the but terflyfishes. During the past 15 years, chaetodontid species richness has been stable in the lagoon and on the external slope of Moorea alth ough a few coral-eating species seem to be regressing, following chang es in the coral community, while at least one species seems to be expa nding its distribution.