Distribution of demersal fishes along the US west coast (Canada to Mexico) in relation to spatial fishing closures (2003-2011)

A temporally and spatially variable Rockfish Conservation Area (RCA) was established as a marine protected area along the US west coast in 2002 to protect stocks of rockfishes Sebastes spp. Since the RCA falls within the region sampled annually by the West Coast Groundfish Bottom Trawl Survey, we utilized data collected from 2003 to 2011 to evaluate whether establishment of the RCA influenced catch per unit effort (CPUE), species richness, and size distribution of demersal fishes. We compared CPUE and species richness among 3 management areas (continuously closed, periodically closed, and open to commercial bottom trawling) using analysis of covariance models that account for variability due to area, year, and depth. The most appropriate models for CPUE (35 species treated individually and aggregated into 6 subgroups) and species richness were selected using Akaike's information criterion. All of the best-fit models were highly significant (p < 0.0001), explaining 3 to 76% of the variation in catch. For 27 species and 5 subgroups, mean CPUE was significantly greater within the area continuously closed to commercial bottom trawling relative to areas periodically closed or open. The most appropriate model for richness included area and year, and mean richness was greatest in the area continuously closed to trawling. Species-specific length composition distributions were calculated from subsampled individual lengths for 31 species. Significant differences in length frequency distributions were observed, with a higher proportion (similar to 65%) of larger fish most often present in areas continuously closed to commercial bottom trawling (20 of 31 species) relative to other areas. Our data suggest that the RCA is an effective management tool for conserving not only rockfishes, but also other demersal fish species.