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AFSC/RACE/MACE: Results of 2010 Pollock Acoustic-Trawl Survey Bering Sea- DY1006
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Eastern Bering Sea shelf walleye pollock (Theragra chalcogramma) abundance and distribution
in midwater were assessed between 5 June and 7 August 2010 using acoustic-trawl techniques
aboard the NOAA ship Oscar Dyson. The survey also assessed walleye pollock in the
Cape Navarin area of Russia. Results showed that ocean surface temperatures were warmer
in 2010 than in recent years (1.8° ? 12.3°C in 2010 vs. 0.7° ? 8.3°C in 2008 and 0.9°
? 8.9°C in 2009). The majority of the pollock biomass in the U.S. Exclusive Economic
Zone (EEZ) was located to the south and west of St. Matthew Island between the 100
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 high compared to recent surveys. The 2010
pollock biomass estimate in the U.S. EEZ was 2.323 million metric tons (t). The 2009
biomass was 0.924 million t and the estimated 2008 biomass was 0.997 million t. East
of 170° W, the predominant length mode was 40 cm and most ages ranged between 3 and
6 years. In the U.S. west of 170° W (87.4% of total biomass), dominant modal lengths
were 26, 16, and 39 cm, corresponding to pollock aged 2, 1, and 4, respectively. In
Russia (5.3% of total biomass), modal lengths and ages were generally similar to those
in the U.S. west of 170° W. Vertical distribution analyses indicated that 85% of adult
biomass was within 40 m of the seafloor. Juveniles were found both near the seafloor
and higher in the water column; 65% of juvenile biomass was within 40 m of the seafloor
while 13% was within 45 m of the surface. Finally, the first field tests of a non-extractive
stereo camera-trawl system (Cam-Trawl) were successfully completed during the 2010
survey, and the multifrequency euphausiid backscatter index of abundance was successfully
computed, indicating a reduced abundance of euphausiids compared with that in summer
2009.
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