Gill parasites of Cephalopholis argus (Teleostei : Serranidae) from Moorea(French Polynesia): site selection and coexistence

The distribution and coexistence of gill ectoparasites of 121 specimens of Cephalopholis argus Bloch et Schneider, caught between October 1994 and Oct ober 1995, were investigated. Adults of the monogenean Benedenia sp. and co pepod Hatschekia sp., the larval caligid copepod Caligus sp. (copepodite an d chalimus stages), and praniza larvae of the isopod Gnathia sp. were found . All species were aggregated within the host population. Infracommunities were poor, with only 40.5% of fish infected by two parasite species. Only t wo individual fish harboured all the parasite species observed at the compo nent community level. Prevalences were less than 50% and mean intensities w ere low (less than 6 parasites/host). No dominant parasite species were obs erved in the host population. The spatial distribution of each parasite spe cies was studied on different partitions of the gill arches. Adult parasite stages that are mobile showed much overlap in their distribution, whereas temporarily attached larvae of Caligidae were more site specific. Copepodit e and chalimus larvae showed niche restriction that is probably due to greg arious behaviour. Positive associations between caligid larvae reflected in traspecific interaction for site and/or resources. Each of the Caligus sp. larval stages prefers specific sites, as do the adults, which occur exclusi vely in the buccal cavity of the host. Infracommunities were too poor and t oo few to induce processes of interspecific competition.