The 1999 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 1999. The survey area stretched from the U.S.-Canada border (near Nitinat Canyon) to 34°30'N lat. (near Pt. Arguello) in waters from 183 to 1,280 m deep. This was the eleventh survey in an ongoing series to monitor long-term trends in the distribution and abundance of WCUCS groundfish populations. This was the second year that spatial coverage of the WCUCS groundfish trawl survey was expanded to include all of the International North Pacific Fisheries Commission (INPFC) statistical areas between Point Conception (34°30’N lat.) and the U.S./Canada border. Sampling was conducted aboard the NOAA ship Miller Freeman. We successfully sampled 199 of the 208 stations that we established during the 1997 and previous WCUCS surveys. Survey catches included 142 different species of fishes from 55 fish families and 246 different invertebrates representing 12 phyla and 24 classes. Only 146 of the invertebrates were identified to the species level. With all depth strata and INPFC areas combined, Dover sole (Microstomus pacificus), longspine thornyhead (Sebastoblobus altivelis), and spiny dogfish (Squalus acanthias) had the highest catch rates. Spiny dogfish were the most abundant in the U.S.-Vancouver and Columbia INPFC areas and Dover sole and longspine thornyhead had higher catch rates in the Eureka, Monterey, and Conception INPFC areas when all depths were combined. The biomass estimates for 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 105,520 metric tons (t), 46,230 t, 95,795 t, and 25,295 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 and catch rates of fish and invertebrates.


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