NOAA Technical Memorandum NMFS Series

The Northwest Fisheries Science Center of the National Marine Fisheries Service, NOAA, uses the NOAA Technical Memorandum NMFS series to issue informal scientific and technical publications when complete formal review and editorial processing are not appropriate or feasible due to time constraints. Documents published in this series may be referenced in the scientific and technical literature.

The NMFS-NWFSC Technical Memorandum series of the Northwest Fisheries Science Center continues the NMFS-F/NWC series established in 1970 by the Northwest & Alaska Fisheries Science Center, which has since been split into the Northwest Fisheries Science Center and the Alaska Fisheries Science& Center. The NMFS-AFSC Technical Memorandum series is now being used by the Alaska Fisheries Science Center.

Reference throughout this document to trade names does not imply endorsement by the National Marine Fisheries Service, NOAA.

This document should be cited as follows:

Turk, T.A., et. al. 2001. The 1998 Northwest Fisheries 
Science Center Pacific West Coast upper continental
slope trawl survey of groundfish resources off Washington,
Oregon, and California. U.S. Dept. Commer., NOAA
Tech. Memo. NMFS-NWFSC-50, 122 p.

Most NOAA Technical Memorandums NMFS-NWFSC are
available on-line at the Northwest Fisheries Science Center
web site (http://www.nwfsc.noaa.gov)

Copies are also available from:

National Technical Information Service
U.S. Department of Commerce
5285 Port Royal Road
Springfield, VA 22161
phone orders (1-800-553-6847)
e-mail orders (orders@ntis.fedworld.gov)

This HTML file represents the Introduction only; the rest of the document is available only in PDF format.

EXECUTIVE SUMMARY

In 1998 the Northwest Fisheries Science Center (NWFSC), initiated a new bottom trawl survey of the commercial groundfish resources in the slope zone (100 - 700 fathoms [fm]; 183 - 1,280 meters [m]) of the continental U.S. West Coast (Washington, Oregon, and California) chartering local West Coast trawlers. The survey was conducted from Cape Flattery, Washington (48°10' N), to Morro Bay, California (35°N), between August 20, 1998 and October 16, 1998.

An Aberdeen-style net with a small-mesh (2" stretched measure or less) liner in the codend (to retain pre-recruits) was used to sample fish biomass. The tow duration of each haul was targeted for 15 minutes. Tow duration was measured as the simple difference between the times marking touchdown and lift-off of the trawl net from the seafloor.

Survey-sampling locations were arranged along east-west transects of latitude. Transects were designated to be separated by 10 minutes of latitude. There were 80 such transects in total, covering the coast between the survey endpoints. Five stations in each transect were selected from two categories: shallow (100 - 300 fm), and deep (300 - 700 fm). The category with the greatest linear distance was assigned three randomly-selected depth ranges to sample, while the category with the lesser linear distance was assigned two randomly-selected depth ranges to sample. Out of a total of 400 possible sampling locations, attempts at sampling were made in 347 of these. Of the stations in which sampling was attempted, 302 tows were successful. Simrad ITI or Scanmar net-mensuration data, as well as GPS course and position data, were obtained from 296 of the successful tows. Bottom-contact sensor data was obtained from 291 of the successful tows.

Catches were sorted to species level or to other appropriate taxon levels and then weighed using an electronic, motion-compensated scale. Sampling efforts were concentrated on the four Dover-sablefish-thornyhead (DTS) complex species: 1) Dover sole, 2) sablefish, 3) shortspine thornyhead (SST), and 4) longspine thornyhead (LST). Dover sole and sablefish were separated by sex and a total of up to 125 - length measurements per haul were collected from each species for both sexes combined. A total of 48 species or families were identified over the entire survey area.

ACKNOWLEDGMENTS

We would like to thank the FV Sea Eagle, the FV Pacific Sun IV, the FV Blue Horizon, the FV Amy Lynn, and the scientific crew for their hard work during the 1998 NWFSC West Coast groundfish slope survey. The scientific crew included (in alphabetical order) Jon Brodziak, Tonya Builder, Dan Erickson, Dan Kamikawa, Nick Lowry, Marion Mann, Bruce McCain, Jennifer Menkel, Bruce Pedersen, Jean Rogers, Teresa Turk, John Wallace, and Bill West. We are also grateful to many people at the Resource Assessment and Conservation Engineering (RACE) and Resource Ecology and Fisheries Management (REFM) Divisions of the Alaska Fisheries Science Center (AFSC). They include Bob Lauth, Robin Harrison, Peter Munro, Michael Martin, and Sarah Gaichas who assisted us on details of the survey operations and planning; and Scott McEntire for creating the bottom contact sensor (BCS) and assisting us in our use of this very valuable instrument. Also, thanks to the net loft crew at the AFSC for refurbishing our nets, making the splitting nets, and supplying the net accessories used for this survey. We would also like to express our appreciation Mary Breaker and Mary Craig for their logistical shore-side support.

The rest of the document is available in PDF format.