The 1997 Pacific West Coast upper continental slope trawl survey of groundfish resources off Washington, Oregon, and California: Estimates of distribution, abundance, and length composition

Abstract

The Alaska Fisheries Science Center's Resource Assessment and Conservation Engineering Division (RACE) conducted a groundfish bottom trawl survey of the West Coast upper continental slope (WCUCS) in 1997. The survey area stretched from the U.S.-Canada border (near Nitinat Canyon) to 34°50'N lat. (near Pt. Arguello) in waters from 183 to 1,280 m deep. This was the tenth survey in an ongoing series to monitor long-term trends in the distribution and abundance of WCUCS groundfish populations. The spatial coverage of the WCUCS groundfish trawl survey was expanded in 1997 to include all of the International North Pacific Fisheries Commission statistical areas between Point Conception (34°30'N lat.) and the U.S./Canada border. Sampling density was reduced to one-third the density of previous surveys so that the expanded area could be surveyed within a 5-week period. Sampling was conducted aboard the NOAA ship Miller Freeman. We successfully sampled 182 of the 200 stations that we had previously established.

Catches included 149 different species of fishes from 55 fish families. Two-hundred and twelve different invertebrates representing 10 phyla and 18 classes were caught but only 125 of these invertebrates were identified to the species level. With all depth strata combined and when all INPFC areas and depths were combined, Pacific whiting (Merluccius productus) and spiny dogfish (Squalus acanthias) had the highest catch rates in the U.S.-Vancouver, Columbia, and Eureka INPFC areas. In the Monterey and Conception INPFC areas, Dover sole (Microstomus pacificus), longspine thornyhead (Sebastoblobus altivelis), Pacific whiting, and sablefish (Anoplopoma fimbria) had the highest catch rates when all depths were combined. The biomass estimates for the Dover sole, sablefish, longspine thornyhead, and shortspine thornyhead (Sebastolobus alascanus) varied by stratum and INPFC area. The total biomass estimates for all INPFC areas and strata combined were 109,858 t, 71,019 t, 101,636 t, and 26,393 t for Dover sole, sablefish, longspine thornyhead, and shortspine thornyhead, respectively The survey design and the methods used are described, the data collected are summarized, and the results of analyses of distribution, abundance, and biological parameters are presented. Data on water temperature, catch composition, relative abundance, and geographic distribution are reported. Estimates of biomass, population abundance, and length composition are also presented. Appendices include position and catch listings for each haul, catch rates of fish and invertebrates, and population size compositions.


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