SPATIAL AND TEMPORAL PATTERNS IN ASSEMBLAGES OF TEMPERATE REEF FISH

For reef fish in temperate marine regions, such components of local assemblage diversity (i.e., within a reef) as species richness, total fish 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 species, overall species richness was affected only moderately by major oceanographic disturbances, This resilience of the assemblage is in marked contrast to high temporal variation in densities exhibited by many local populations of individual species, and it suggests that measurements of diversity to indicate status of an assemblage should be used with 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. Mechanisms that can ''buffer'' local diversity of reef fishes include dispersal of young that inter-connects subpopulations, high ''inertia'' in relative abundance and population structures (especially for long-lived species), and broad ecological requirements of many species. These considerations suggest that the effect of disturbances on local diversity of reef fishes will depend in part on the magnitude, duration, frequency and spatial scale of the perturbation. While long-term data are few, available information suggests that, due to life history characteristics of the fish and the spatial and temporal scales at which disturbances are likely to occur, assemblages of temperate marine reef fish might be relatively resilient to environmental perturbations.