Resource Assessment and Conservation Engineering (RACE) Division

GROUNDFISH ASSESSMENT:
Summer Field Season Begins

The chartered fishing vessel Vesteraalen. (Photo by Jay Orr.)

Every year since the mid-1970s, biologists in the Groundfish Task of the Resource Assessment and Conservation Engineering (RACE) Division have gathered their equipment and boarded chartered trawlers to conduct bottom trawl surveys of groundfish and invertebrate populations in the eastern Bering Sea, Aleutian Islands, Gulf of Alaska, and, until 2002, off the west coast of the "Lower 48". These surveys employ trawl nets which sweep the bottom at preselected stations, collecting samples of demersal fish and invertebrates. Catches range in size and diversity from less than 100 kg of a variety of species to virtually pure catches of a single species weighing many tons. Once catches are brought aboard, biologists sort the catch by species, weigh and count samples of all species, measure the length and weight of specimens of commercially or ecologically important species, and collect a wide variety of biological samples and data.

In recent years, more focus has been given to sorting and identifying invertebrates and rare or unusual fish species. The RACE Division has partnered with other institutions to provide expertise and identification, particularly of invertebrate taxa. These partnerships have been mutually beneficial, helping us to identify rare species and even discovering previously undescribed species. During surveys in the Gulf of Alaska and Aleutian Islands, where we use a net with a protective "roller gear" footrope, we deploy a small sampling net, dubbed a "benthic bag", attached to the footrope of the trawl to collect qualitative samples of small animals or shells that may not be caught by the main trawl. The benthic samples help scientists classify and evaluate the habitat, as well as collect specimens of demersal fauna without subjecting them to the crushing that occurs in the codend of the main net.

Most RACE bottom trawl surveys last approximately 2½ months and are divided into three or four legs of approximately 3 weeks each. Workdays in the field can average about 12 hours, 7 days a week.

by Mark Wilson.

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AFSC Quarterly
Research Reports
April - June 2003