DISTRIBUTION OF BOTTOM-TRAWL FISH ASSEMBLAGES OVER THE CONTINENTAL-SHELF AND UPPER SLOPE OF THE US WEST-COAST, 1977-1992

Twenty-three bottom-trawl fish assemblages were identified from the re lative biomass of 33 dominant species that occurred in the National Ma rine Fisheries Service's triennial trawl surveys over the continental shelf and upper slope off California, Oregon, and Washington from 1977 to 1992. The assemblages accounted for about 70% of the total variati on in species composition among 2565 hauls. Although the assemblages p ersisted over the 15-year study period and occurred within broad geogr aphic boundaries, some had substantially different spatial distributio ns among surveys. The ability to differentiate assemblages across five environmental variables (latitude, depth, surface and bottom water te mperatures, and surficial substrate) was low. The preponderance of bak e-dominated assemblages throughout the study area suggests that Pacifi c bake (Merluccius productus) may play a large role in the dynamics of demersal fish communities off the west coast of the United States.