Microhabitat association and temporal stability in reef fish assemblages on massive <Emphasis Type="Italic">Porites</Emphasis> microatolls

A massive Porites microatoll generally has three types of microhabitat at the top, side, and base of the microatoll. The purpose of the present study was to analyze microhabitat associations of reef fish on microatolls to determine whether habitat characteristics play an important role in the structuring of reef fish assemblages in a patchy habitat. We also investigated temporal stability of reef fish assemblage structures over a period of 17 months to determine whether fish assemblage structures vary in a random manner. The results of correspondence analysis indicated species-specific habitat associations for pomacentrids (five species) and labrids (seven species). The degree of temporal stability of fish assemblage structures, calculated by Piankas index, was relatively high in a large-sized microatoll (0.503–0.831: 3.6m in diameter), in which microhabitat associations of fishes were clearly observed. The present study suggests that a microhabitat association is one of the important factors responsible for organization of reef fish assemblages in a microatoll.