Biomass survey of rockfish stocks off the southwest coast of Vancouver Island, September 8-22, 1985 (M/V Howe Bay) / by B.M. Leaman, G.E. Gillespie, D.A. Nagtegaal, and R.D. Stanley. : Fs97-6/1611E-PDF

"The M/V HOWE BAY was used to replicate a 1979 M/V ARCTIC HARVESTER trawl survey of rockfish (Sebastes spp.) stocks off the southwest coast of Vancouver Island and in U.S. waters off Cape Flattery (approximately 48°4'N to 49°25'N). Seventy-five hauls were completed. Catch rates for nearly all species were notably reduced from 1979 levels, with the catch rates of the four most prevalent species from the 1979 survey falling 80-90%. The 1985 total rockfish biomass estimate of 3,480 t is 49% of the 1979 estimate. Catch rates for Pacific ocean perch (S. alutus) decreased 79% from 1979 levels. The size frequencies of S. alutus showed only a slight increase in modal lengths, and no evidence of substantial recruitment. Behavioral characteristics of rockfish and the characteristics of trawl surveys make absolute estimates of rockfish biomass unreliable, as catch rates may vary highly on the same site through different periods of the day. They are more useful as relative indicators of population trends, in conjunction with other methods. The relative decrease in estimated biomass of S. alutus, when viewed with the lack of recruitment of young perch and the decreases in commercial (84%) and research (59%) catch rates during 1979-1985, indicates further deterioration of the stock, already in poor condition in 1979"--Abstract, page iii.

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