Cohabitation of Competing Territorial Damselfishes on a Caribbean Coral Reef

Individual adults of three Caribbean damselfishes defend feeding areas that do not overlap with those of conspecific adults. The feeding areas of adults of the two smaller species, Stegastes dorsopunicans and S. Planifrons, do not overlap interspecifically. However, feeding areas of adults of the largest species, Microspathodon chrysurus, are superimposed on feeding areas of adults and juveniles of the two Stegastes species. The large species aggressively dominates its smaller interspecific cohabitants. Cohabitant individuals of each species eat the same types of benthic microalgae. M. Chrysurus has the same daily cycle of feeding activity as the two small species, uses the same feeding microhabitats as they do, and feeds almost exclusively in their feeding areas. Cohabitants defend their feeding areas against the same set of other herbivorous fishes, but M. Chrysurus is involved in defensive actions much less frequently than is either of its small cohabitants. M. Chrysurus also is much less effective at such defense than at least one cohabitant, S. Dorsopunicians. S. Dorsopunicans on a reef from which M. Chrysurus were removed increased their body mass more and had larger fat deposits than conspecifics on a control reef. Thus adults of M. chrysurus appear to be dependents that use their size—based dominance ability to obtain food from their cohabitants. Juveniles of M. Chrysurus and S. Dorsopunicans exhibit small—scale habitat segregation and segregated use of feeding substrates in a shared microhabitat, which may facilitate the recruitment of both species.