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NOAA Technical Memorandum NMFS-AFSC-372

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The 2017 eastern Bering Sea continental shelf and northern Bering Sea bottom trawl surveys: Results for commercial crab species

Abstract

The eastern Bering Sea bottom trawl survey has been conducted annually since 1975 by the Resource Assessment and Conservation Engineering Division of the Alaska Fisheries Science Center, National Marine Fisheries Service. The purpose of this survey is to collect data on the distribution and abundance of crab, groundfish, and other benthic resources in the eastern Bering Sea. These data are used to estimate population abundances for the management of commercially important species in the region. This document includes the time series of results from 1975 to the present. In 2017, 395 total stations (375 standard stations and 20 resampled stations in Bristol Bay) were sampled on the eastern Bering Sea shelf from 4 June to 15 August. In early June, colder bottom temperatures extended into Bristol Bay creating the need to resample 20 stations due to delaying effects of cold water temperature on red king crab reproductive cycle. There was an overall decrease in biomass and abundance in male red king and blue king crab and female red king crab. There was an overall increase in immature female blue king crab and a decrease in mature female biomass and abundance, with no mature female blue king crab being caught in the St. Matthew Island Section. There were overall increases in immature and legal male and immature and mature female biomass and abundance in Chionoecetes bairdi and C. opilio crab, and a decrease in mature male biomass and abundance in Chionoecetes bairdi and C. opilio crab.

In addition to the standard eastern Bering Sea survey, in 2017, following the conclusion of the standard survey, 145 stations were sampled in the northern Bering Sea region, encompassing the region south of Bering Strait and including Norton Sound. These stations were sampled between 1 August and 2 September. We report the results of this survey separately from the eastern Bering Sea survey, within the northern Bering Sea section of this report. Blue king crabs occurred largely in the region north of St. Lawrence Isand, in greater densities than were observed for the St. Matthew and Pribilof stocks. Red king crab occurred primarily in Norton Sound, at densities roughly intermediate between those generally observed in the Bristol Bay and Pribilof Districts. Chionoecetes opilio dominated the catch, with the highest densities observed during the 2017 Bering Sea survey occurring to the south of St. Lawrence. Immature male and female opilio were predominate, although mature females were observed, primarily along the western edge of the survey grid, and in the north, near Bering Strait. Morphometrically mature (“large-clawed”) male C. opilio were scattered throughout the survey region, but most prevalent within catch near Bering Strait.

 




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