Factors affecting fish diversity on a temperate reef: the fish assemblage of Palos Verdes Point, 1974–1981

Synopsis

We conducted underwater fish assemblage surveys, benthic quinaldine sampling, and ichthyoplankton collections over high and low relief reefs at Palos Verdes Point, California from 1974 through 1981. Seventy-three species (adults and larvae) were collected or observed at Palos Verdes. Of the 24 most abundant species, 8 showed significant abundance trends correlated with changes in sea surface temperatures; four increasing, and four decreasing. Two taxa occurred predominantly in the kelp canopy, while seven others were distributed at least 20% of the time between the canopy and the bottom. There was little significant change in the Palos Verdes benthic fish assemblage with development of the kelp bed. Only the kelp bass, Paralabrax clathratus, showed a significant increase in abundance that correlated with the kelp bed formation. Similarly, we did not note an increase in juvenile fish during this period. In general, we suggest that the presence or absence of kelp has little effect on the abundance of most fish species in a high relief environment. Analysis of our data and that of other studies indicate that kelp bed fish assemblages within the Southern California Bight vary in a south-north direction. The Palos Verdes Point kelp bed appears to be more productive than those nearer the limit of the Bight, but was consistently lower in both fish abundance and diversity then the nearby breakwater at King Harbor. This difference has been maintained even though changes in the species structure at King Harbor has altered sufficiently since 1976 for the two formerly distinct assemblages to be significantly concordant.