ABSTRACT: We examined the roles of interspecific competition and habitat preference in determining the distribution of 2 anemonefish species, Premnas biaculeatus and Amphiprion melanopus, among the 2 morphs of the anemone Entacmaea quadricolour. This anemone species has a solitary morph which is usually occupied by a single pair of P. biaculeatus and a colonial morph which is usually occupied by large social groups of A. melanopus. The possibility that interspecific competition, and/or preference of adults of each species of fish for the anemone morph it usually occupies, determines this distribution was tested using aquarium based experiments. Adults of one species, A. melanopus, displayed a preference for the anemone morph it usually occupies in the field, but P. biaculeatus did not. Instead, P. biaculeatus pairs tended to associate closely, always occupying the same anemone regardless of the morph chosen. While interspecific competition limited fish abundance within anemones, competitive interactions could not explain the distribution of fish species among anemone morphs. That is, neither fish species displaced the other more often on the anemone morph it usually occupies in the field. While juvenile P. biaculeatus exhibit some preference for solitary morphs and A. melanopus appear to prefer colonial morphs, juvenile distributions cannot fully explain the distribution of adults. Instead, we suggest that adult distributions are explained by a combination of juvenile habitat preferences, adult-juvenile interactions and constraints imposed by the contrasting social systems of the 2 species.

KEY WORDS: Habitat selection · Interspecific competition · Distribution · Specialisation · Coral-reef fish · Anemonefish · Amphiprion melanopus · Premnas biaculeatus

Published in MEPS Vol. 186 (1999) on September 17
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1999