Schabetsberger, R. Alaska Fisheries Science Center, NOAA,
Brodeur, R. Alaska Fisheries Science Center, NOAA, Ric.Brodeur@noaa.gov
Napp, J. Alaska Fisheries Science Center, NOAA, Jeff.Napp@noaa.gov
DIEL VERTICAL MIGRATION, FEEDING SELECTIVITY, AND PREY DISTRIBUTION OF JUVENILE WALLEYE POLLOCK AT A PRODUCTIVE FRONTAL REGION IN THE EASTERN BERING SEA
We studied diel vertical migration of age-0 walleye pollock (Theragra chalcogramma) at an inner shelf frontal region near St. Paul Island, Bering Sea. Acoustic data collected at 38 and 120 kHz revealed distinct diel vertical migrations of juvenile pollock from daytime depths of 40 m to less than 20 m at night. Juvenile pollock dominated (97% by number) the catch of midwater trawls which targeted layers of strong acoustic backscatter. Distributions of target strengths (TS) recorded from the depth through which the trawl fished corresponded well with predicted values based on empirical length/TS relationships for age-0 walleye pollock. Copepods, euphausiids and chaetognaths exhibited strong diel vertical migrations whereas cnidarians did not. Feeding selectivity (E*) did not change over the diel period and was positive for copepods and negative for all other prey taxa. Chaetognaths dominated the zooplankton catches, but were generally lacking from pollock diet. Pollock showed positive selection for euphausiids with increasing size.
Day: Thursday, Feb. 4
Time: 11:00 - 11:15am
Location: Hilton of Santa Fe