Colonization by nearshore fish on small artificial reefs in Barkley Sound, British Columbia

Abstract

We investigated the structure of a temperate nearshore fish community by examining the development of fish assemblages on small artificial reefs of concrete blocks constructed in two series 6 months apart. In each series, a species equilibrium, of approximately six species, was rapidly reached within 6 months. Eight of the 30 species which had colonized the reefs from the surrounding rocky habitats were common on the reefs. Both juveniles and adults of all species were present, except for the rockfishes (Sebastes spp.) which were represented only by young individuals (1 to 3 years of age). Tagging indicated that the bottom-dwelling species (Gobiidae, Cottidae) remained permanently on the reefs, whereas a seasonal turnover in rockfish occurred.The communities inhabiting the reefs usually did not differ from each other within each series, whereas significant differences occurred between series. This difference was attributed to the differential colonizing ability of species. No evidence of interspecific competition was apparent among the species inhabiting the reefs.The results are discussed in light of some current models of coral reef fish community structure. Some possible factors affecting the differences observed between tropical and temperate waters are also discussed.