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Results of the Acoustic-Trawl Survey of Walleye Pollock (Gadus chalcogrammus) on the U.S. and Russian Bering Sea Shelf in June - August 2014 (DY1407)
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08/01/2015
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Series: AFSC processed report ; 2015-07
[PDF-2.73 MB]
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Description:Eastern Bering Sea shelf walleye pollock (Gadus chalcogrammus) midwater abundance and distribution were assessed from Bristol Bay in the United States, to Cape Navarin, Russia, between 12 June and 13 August 2014 using acoustic-trawl survey methods aboard the NOAA ship Oscar Dyson. Water column temperatures were warm in 2014 compared with the cold temperatures of the past several survey years (2006-2012). Most walleye pollock biomass was distributed relatively evenly across the shelf from a region north of Unimak Island to Navarin Canyon, between roughly the 50 m and 1,000 m isobaths. Estimated pollock biomass in midwater (between 16 m from the sea surface and 3 m off bottom) in the U.S. EEZ portion of the Bering Sea shelf was 3.439 million metric tons (t), nearly twice the 2012 estimate (1.843 million t) and the highest that has been observed since 2002. Pollock biomass east of 170°W was 1.425 million t (40% of the total shelf-wide), with 2-year-old pollock (26 cm modal fork length (FL)) comprising 55% of that biomass. Pollock biomass in U.S. waters west of 170°W was 2.013 million t (57% of total shelf-wide biomass), consisting primarily of pollock aged 1, 2, and 4-6 years (15, 26, and 38 cm dominant modal FL, respectively). Two-year-old pollock were more abundant east than west of 170° W and contributed to an eastward shift in distribution of U.S. pollock biomass compared with recent years. Estimated numbers of 2-year-old pollock also surpassed the numbers estimated for the strong 2008 year class in 2010, although the 2008 year class was still evident in the population. In Russia (104 thousand t, 3% of total biomass), primarily 4-year-old fish (38 cm modal FL), were observed, with proportionally fewer 1- and 2-year-olds than observed west of 170° W in the United States. The preliminary spatial distribution of euphausiid backscatter is presented, but analyses are still in progress.
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