NOAA Technical Memorandum
NMFS-AFSC-49
Data report: 1990 Gulf of Alaska bottom trawl survey
Abstract
The third triennial groundfish assessment survey of the Gulf of Alaska was conducted during the summer of 1990 by the Alaska Fisheries Science Center's Resource Assessment and Conservation Engineering (RACE) Division and the Auke Bay Laboratory (ABL). Two chartered trawlers, the Pat San Marie and Green Hope and the National Oceanic and Atmospheric Administration research vessel Miller Freeman successfully sampled 708 survey stations in the Gulf of Alaska from the Islands of Four Mountains (170°W long.) to Dixon Entrance (133°25' W long.) in depths less than 500 m using standard RACE Division Nor’eastern high-opening bottom trawl nets with rubber bobbin roller gear. This document combines the results of the RACE and ABL surveys.
The survey design divided the overall Gulf of Alaska survey area into 49 strata based on bathymetric and geographic features to produce a standard survey area totaling approximately 87,000 square nautical miles (nmi2) (296,700 km2 ) ranging in bottom depth from 1 to 500 m. Trawl samples were allocated among strata in proportion to fish densities observed during the 1984 U.S.-Japan triennial survey. Stations were selected randomly from a 5 by 5 nmi grid of numbered points, superimposed over each stratum. The bottom area swept during each trawl haul was determined from an acoustic trawl mensuration system and Loran navigational equipment.
The species composition was determined for each catch and the principal species were sampled for sex, length, individual weight and age distributions.
Seawater temperatures were collected during trawling. operations. Ancillary collections included specimens for diet studies, juvenile walleye pollock (Theragra chalcogramma) distribution and predator studies, skate taxonomic delineation, fishery observer training and marine mammal prey studies and sightings.
Results include a ranking of catch abundance for the 20 most abundant species, abundance estimates of the principal fish species, distribution, and size composition by geographic location and depth and length versus weight regression parameters. Age composition data are included for walleye pollock and Pacific ocean perch (Sebastes alutus). Seawater surface and bottom temperature data are presented by area. Appendices contain the survey trawl specifications and diagram, strata definitions and charts, list of species encountered and length-weight relationships of the principal species.
Arrowtooth flounder (Atheresthes stomias), walleye pollock, Pacific halibut (Hippoglossus stenolepis) and Pacific cod (Gadus macrocephalus) were the dominant species throughout the survey area. The rockfish, sablefish (Anoplopoma fimbria), soles and other species were locally abundant in some areas. Red squid (Berryteuthis magister) was the most abundant invertebrate throughout the survey area.
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