SPATIAL AND TEMPORAL PATTERNS IN ASSEMBLAGES OF TEMPERATE REEF FISH

For reef fish in temperate marine regions, such components of local as semblage diversity (i.e., within a reef) as species richness, total fi sh density, and rank order of abundance can remain relatively constant through time. Long-term data (17 years) for assemblages on 2 reefs in Southern California revealed that, despite high turnover in rare spec ies, overall species richness was affected only moderately by major oc eanographic disturbances, This resilience of the assemblage is in mark ed contrast to high temporal variation in densities exhibited by many local populations of individual species, and it suggests that measurem ents of diversity to indicate status of an assemblage should be used w ith caution. Here we consider various processes and factors, together with the spatial and temporal scales over which they operate, that can influence local diversity (and its estimation) of reef fishes. Mechan isms that can ''buffer'' local diversity of reef fishes include disper sal of young that inter-connects subpopulations, high ''inertia'' in r elative abundance and population structures (especially for long-lived species), and broad ecological requirements of many species. These co nsiderations suggest that the effect of disturbances on local diversit y of reef fishes will depend in part on the magnitude, duration, frequ ency and spatial scale of the perturbation. While long-term data are f ew, available information suggests that, due to life history character istics of the fish and the spatial and temporal scales at which distur bances are likely to occur, assemblages of temperate marine reef fish might be relatively resilient to environmental perturbations.