The 1998 Pacific west coast bottom trawl survey of groundfish resources: Estimates of distribution, abundance, and length and age composition

Abstract 

The Alaska Fisheries Science Center's 1998 West Coast triennial bottom trawl survey was conducted to assess stocks of groundfish inhabiting the continental shelf waters off the coasts of California, Oregon, Washington, and southern British Columbia. This was the eighth survey in an ongoing series to monitor long-term trends in the distribution and abundance of these groundfish populations.

Although the objectives of the 1998 survey were similar to those of the previous surveys in the series, we have made minor changes in the survey design over the years. The four most recent surveys have shifted emphasis away from estimating rockfish abundance, as had been the case from 1977 through 1986, toward better assessing a broader range of groundfish species. The current design also focuses upon precisely estimating the near-bottom component of the Pacific hake (Merluccius productus) and juvenile (age 1+) sablefish (Anoplopoma fimbria) resources. The survey encompassed the coastal waters from Pt. Conception, California, to central Vancouver Island, British Columbia (34-300-49-151N lat.). The depth range of the 1998 survey was the same as that in 1995, which had been extended for more complete coverage of the habitat of slope rockfish. The 1980-92 surveys had covered depths from 55 to 366 m; since 1995, we have

surveyed between 55 and 500 m. A total of 536 stations were occupied, of which 527 were successfully sampled. Catches included 168 different species of fish representing 55 families.

This report documents the survey design and methods used in 1998, summarizes biological and environmental data collected, and presents the results of standard analyses of distribution, abundance, and biological parameters for the commercially important groundfish species in the region. Data on water temperature, catch composition, relative abundance, and geographic distribution are reported. Estimates of biomass, population abundance, length composition and age composition are also presented. Data appendices are located in a separate companion volume.


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