Results of 2012 Pollock Acoustic-Trawl Survey Bering Sea- DY1207

Eastern Bering Sea shelf walleye pollock (Theragra chalcogramma) midwater abundance and distribution were assessed from Bristol Bay in the United States, to Cape Navarin, Russia, between 7 June and 10 August 2012 using acoustic-trawl techniques aboard the NOAA ship Oscar Dyson. Most of the pollock biomass in the U.S. exclusive economic zone (EEZ) was distributed between the Pribilof Islands and Cape Navarin, between roughly the 80 m and 200 m isobaths. Estimated pollock abundance in midwater (between 16 m from the surface and 3 m off bottom) in the U.S. EEZ portion of the Bering Sea shelf was 1.843 million metric tons (t), lower than in 2010 (2.323 million t) but higher than in 2009 or 2008 (0.924 million t, and 0.997 million t, respectively). Pollock biomass east of 170° W was 0.279 million t, the predominant length mode was 47-48 cm, and most ages ranged between 4 and 7 years. In the U.S. waters west of 170° W, pollock biomass was 1.563 million t (65.4% of total shelf-wide biomass), and dominant modal lengths were 23, 38, and 30 cm, corresponding to pollock aged 2, 4, and 3 years, respectively. In Russia (0.550 million t, 23% of total biomass), modal lengths and ages were similar, though generally smaller and younger than those in the U.S. waters west of 170° W. Vertical distribution analyses indicated that whereas 80-90% of the adults were within 50 m of the bottom only about 60% of the juveniles were observed in that depth layer. Results of a paired (midwater-bottom) trawl efficiency comparison project are presented. The preliminary spatial distribution of the euphausiid abundance index is presented, but analyses are still in progress.