Results of the acoustic-trawl survey of walleye pollock (Gadus chalcogrammus) on the U.S. Bering Sea Shelf in June-August 2018 (DY1807)

Details

• Personal Author:
  McCarthy, A. ; Honkalehto, T. ; Lauffenburger, N. ; De Robertis, A.
• Corporate Authors:
  United States. National Marine Fisheries Service ; Alaska Fisheries Science Center (U.S.) ; Resource Assessment and Conservation Engineering Division
• NOAA Program & Office:
  NMFS (National Marine Fisheries Service) ; AFSC (Alaska Fisheries Science Center)
• Description:
  Eastern Bering Sea shelf walleye pollock (Gadus chalcogrammus) midwater abundance and distribution were assessed from Bristol Bay to the U.S.-Russia Convention Line from 6 June to 26 August 2018 using acoustic-trawl (AT) survey methods aboard the NOAA ship Oscar Dyson. In addition to surveying the traditional (core) survey area, we also surveyed a region northeast of St. Matthew (the northern extension). Water column temperatures were cooler in 2018 (mean sea surface temperature (SST) 8.5 °C, bottom temperature 3.7 °C) compared with temperatures during the previous AT survey in 2016 (mean SST 11.4°C, bottom temperature 3.9 °C), but still much warmer than in prior cold years (2006-2014; SST means between 4.9° and 6.8 °C). Walleye pollock biomass was concentrated in the regions north of Pribilof and Zhemchug canyons, and east of Pervenets Canyon, primarily between the 100- and 200-m isobaths. The estimated amount of pollock in midwater (between 16 m from the sea surface and 0.5 m off the sea floor) in the U.S. EEZ core survey area was 5.57 billion fish with a biomass of 2.50 million metric tons (t), less than half of the 2016 estimate of 12.2 billion fish with a biomass of 4.83 million metric tons. This estimate includes the lower water column (3 m to 0.5 m), estimated by combining acoustic and bottom trawl data and previously reported separately. Pollock east of 170° W numbered 1.28 billion fish and weighed 0.74 million t (27% of the total shelf-wide biomass, including the northern extension which represented 9% of shelf-wide biomass). Five- and 6-year-old pollock (43 and 45 cm mean fork lengths (FL), respectively) together composed 77.6% of the biomass east of 170° W. Pollock abundance west of 170° W was 4.29 billion fish weighing 1.75 million t (64% of total shelf-wide biomass). These estimates include an ‘unsampled’ portion of the core area (the three westernmost transects, comprising 6.1% of the core area) which was not surveyed due to ship motor failure. Most pollock west of 170° W were aged 5 and 6 years (42 and 44 cm mean FLs, respectively). The mean biomass-weighted depth of adult pollock (≥ 30 cm FL, age-3+) was 79 m in the region east of 170° W and 97 m west of 170° W. The mean weighted depth of juveniles (< 30 cm FL, ages 1 and 2) west of 170° W (relatively few juveniles were observed east of 170° W) was 106 m, 9 m deeper than adults (97 m). The mean euphausiid abundance estimate for 2018 was similar to that in 2004, a relatively low year in the index.
• Keywords:
  Fish Stock Assessment Marine Resources Conservation Trawls And Trawling Underwater Acoustics Walleye Pollock Fish Stock Assessment Marine Resources Conservation Trawls And Trawling Underwater Acoustics Walleye Pollock
• Series:
  AFSC processed report   2020-07
• DOI:
  https://doi.org/10.25923/7njp-tc70
• Document Type:
  Processed Report
• Place as Subject:
  Bering Sea ; Alaska ; United States
• Rights Information:
  Public Domain
• Compliance:
  Submitted
• Main Document Checksum:
  urn:sha-512:6b7d10a4865f78e0ccbe4a0c4cdfa0e264db0c3235f92f0786de825a9a98e74931d68b0053e0becd4cd5f7f80405f8db4f2a4304d33a79287cfc11a81a0a6f68
• Download URL:
  https://repository.library.noaa.gov/view/noaa/27293/noaa_27293_DS1.pdf
• File Type:
  [PDF - 6.48 MB ]