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Resource Assessment &
Conservation Engineering

(Quarterly Report for April-May-June 1998)

Participation in Alaska Department of Fish and Game Gulf of Alaska Seasonality Study

Members of the Resource Assessment and Conservation Engineering (RACE) Division’s Groundfish Assessment Program participated in the first phase of a Alaska Department of Fish and Game (ADF&G) seasonal bottom trawl study of Marmot Bay off Kodiak and Afognak Islands in the Gulf of Alaska (GOA) 16-25 June aboard the ADF&G research vessel Resolution.  The primary purpose of the study, which includes additional sampling periods scheduled for August and October 1998 and January, March, and June 1999, is to document seasonal trends in depth and inshore/offshore distribution of crab and groundfish resources including Tanner crab (Chionoecetes bairdi),Pacific cod, walleye pollock, arrowtooth flounder, flathead sole, rock sole, yellowfin sole, and skates.  Additionally, the seasonal nature of the sampling design will provide quantitative measures of changes in co-occurrence of the demersal groundfish and crab complex, document the changes in distribution of Pacific cod relative to Federal and state waters, and document intra-annual changes in the distribution of Tanner crab associated with maturation.  Along with these objectives, the ADF&G invited AFSC scientists to conduct ancillary studies including specimen collections, food habit studies, research in seasonal gonad development and size-at-maturity for selected species.  The RACE Division Groundfish Program also recognizes the unique opportunity the seasonality study provides by introducing ADF&G to standard RACE Division sampling protocol which, if implemented, would provide data sets from the ADF&G annual crab/groundfish survey of the western GOA similar to those obtained by the NMFS GOA triennial survey (see “National Marine Fisheries Service/Alaska Department of Fish and Game Trawl Comparison Study,” Quarterly Report, January-February-March 1998).  The Resolution was subsequently equipped with RACE Division sampling gear including sorting and weighing tables, electronic length-frequency units, bottom contact sensors, micro-bathythermographs, and computers and software for length-frequency, catch entry, and other data collections.

Thirty-one bottom trawl samples were completed during the seasonality study with the ADF&G standard 400-mesh Eastern survey trawl at depths ranging from 35 to 250 m. All catches were sampled and processed to obtain species composition by weight for all components of the catch.  Length frequencies were obtained electronically for all commercial groundfish species. Additionally, over 200 Pacific cod stomachs and 325 pollock otoliths were collected for processing at the AFSC.  The August seasonality study will continue the collections begun in June but will expand to include additional species such as flathead sole and arrowtooth flounder.  A reproductive study of Pacific cod and flathead sole is scheduled to begin during the October phase of the seasonality study.

By Eric Brown and Harold Zenger.

West Coast Shelf Triennial Trawl Survey

The eighth triennial bottom trawl survey of groundfish resources of the west coast shelf began on 8 June 1998 aboard the chartered fishing vessels Vesteraalen and Dominator. Survey operations began in the vicinity of lat. 3430’N near Point Conception, California.  Sampling will proceed in a northerly direction and will extend as far north, time allowing, as approximately lat. 49 30’N, off southwest Vancouver Island, British Columbia.  The survey will employ a stratified random design which places approximately 620 predetermined trawl stations into three depth strata between 55 and 500 m along east-west track lines spaced 10 nautical miles (nmi) apart.  The survey will end in Seattle on August 9.

The objectives of the 1998 survey will be similar to recent west coast triennial surveys and will be accomplished through a multi-species assessment approach.  Results of the survey will be used to address current problems being faced by managers and researchers of west coast groundfish stocks.  The objectives of the survey are to:

  1. Describe and assess the demersal component of the Pacific hake, Merluccius productus, resource

  2. Describe and assess the shallow water component of the sablefish, Anoplopoma fimbria, resource, specifically those under 2 years of age

  3. Monitor the abundance, distribution, and biological characteristics of principal rockfish  species, Sebastes spp

  4. Monitor the status of other key groundfish stocks

  5. Collect biological samples from a variety of commercially important species, including several rockfish, lingcod (Ophiodon elongatus), and Pacific halibut (Hippoglossus stenolepis), as well as the primary target species

  6. Collect temperature profiles to relate changes in fish distribution among years to changes in oceanographic conditions.

By Russ Nelson.

Annual Bering Sea Bottom Trawl Survey

The chartered fishing vessels Aldebaran and Arcturus departed Dutch Harbor, Alaska, on 6 June to conduct a standard bottom trawl assessment survey of groundfish and crab resources of the eastern Bering Sea shelf.  Trawling operations began at the eastern edge of Bristol Bay and will cover the eastern Bering Sea continental shelf from inner Bristol Bay to the shelf break, and between Unimak Pass to north of St. Matthew Island.  Upon completion of the standard bottom trawl survey, the Aldebaran will conduct a trawl survey of Pavlov Bay and the Arcturus will conduct tests of a towed video system to be used in future studies of the impact of fishing gear on the seafloor.  The Aldebaran and Arcturus will complete operations in Dutch Harbor on 13 and 15 August, respectively.  The standard survey consists of approximately 380 sampling stations positioned on a 20-nmi by 20-nmi grid.

The primary objective of the survey is to continue the annual series of assessment surveys of crab and groundfish resources of the eastern Bering Sea to provide information for:

  1. The North Pacific Fishery Management Council on the distribution, abundance, and biological condition of important groundfish and crab resources

  2. The U.S. fishing industry on catch-per-unit effort and size composition

  3. The support of ongoing studies of the biology, behavior, and dynamics of key ecosystem components.

By Russ Nelson.

Trawl Positioning Gear Trials

Gear trials to evaluate the accuracy of three ultra-short baseline (USBL) systems which could be used in providing real-time information on the geographic location of bottom trawls on the seafloor were conducted aboard the chartered fishing vessel Vesteraalen in Dabob Bay, Hood Canal, Washington, 18-29 May 1998.  Accurate information on trawl location are important to research on the impacts of fishing gear on the seafloor.  The ability to resample specific areas is essential to experimental work planned for the Bering Sea in future years.

The primary research objective was to compare the performance of three acoustic systems that could be used for real-time positioning of a bottom trawl net.  Accuracy of each system will be quantified and compared through trawling within the U.S. Navy’s Naval Undersea Warfare Center’s (NUWC) fixed underwater tracking range in Dabob Bay.  The Dabob Range is a fixed short baseline (SBL) hydrophone array operated by the NUWC to test and evaluate weapon systems, ships, research and development, and fleet training.  USBL systems from three vendor’s (Kongsberg Simrad, Nautronix, Inc., and ORE International, Inc.) were installed, calibrated, and tested during the gear trials.   Data were successfully obtained from each of the three systems and are currently being analyzed.

By Russ Nelson.