Habitat-dependent recruitment of two temperate reef fishes at multiple spatial scales

Abstract

The distribution and abundance of reef fishes has often been attributed to several pro- cesses that result in some measure of recruitment success (settlement and survival of young individ- uals). We employed a large-scale experimental rocky reef system to examine patterns of recruitment of 2 fishes, the California sheephead Semicossyphus pulcher and the blackeye goby Rhinogobiops nicholsii. We quantified recruitment over a 2 yr period on 21 experimental reefs (each 1600 m 2 ) that represented low, medium, and high treatments of habitat coverage. Recruitment of California sheep- head was higher on reefs of medium habitat coverage than on reefs with other coverages, while the blackeye goby exhibited lower recruitment on reefs of low coverage than on reefs with other cover- ages. Within reefs, recruitment to 'edge' habitat was lower than 'inside' the reef for each species. At the smallest scale, several measures of habitat structure were quantified within 1 m 2 quadrats to iden- tify microhabitat characteristics that might explain the distribution of recruits. Rugosity was an important characteristic for predicting the presence of recruits for each species at this small scale. The densities of recruits of California sheephead among treatments of habitat corresponded to the densi- ties of Age 1+ (individuals which recruited during the previous year) california sheephead among treatments the following year, suggesting that spatial patterns of abundance may be established early in life. The abundance of predators did not appear to influence the patterns of recruitment observed for either species. Low densities of recruits for each species may have led to the patterns of recruitment observed through the processes of habitat selection at settlement and density- independent mortality. Longer temporal studies covering variable recruitment are needed to determine the importance of habitat structure relative to other processes.