Random placement and the distribution of fishes among coral patch reefs

On the basis of repeated censuses of unmanipulated assemblages of fish on 20 lagoonal patch reefs.Sale & Douglas (1984) proposed a simple random placement model to account for the structure of such reef fish assemblages.The present paper uses their data augmented by additional censuses and a series of simulation models to explore the adequacy of their proposal.The distributions of a small proportion (about 8 species) of the 143 species recorded on the reefs, but including some of the most abundant species, could not be explained by a process of random colonization.These species vary greatly in abundance among censuses, and tend consistently to prefer certain reefs.The remaining species, while clearly possessing some microhabitat requirements, and perhaps responding to each other's presence, show distribution across patch reefs which are satisfactorily explained by a model of random placement of juveniles from a pool of potential colonists.