Interaction between the vertical distribution of juvenile walleye pollock Theregra chalcogramma
ABSTRACT: In autumn 1984 the interaction of vertical migration of age-0 walleye pollock Theragra chalcogramma m the eastern Bering Sea, and cannibalism was examined. Patterns of verhcal migration were Inferred from acoushc observations, midwater trawls, and occurrence of juveniles in the stonlachs o...
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| Format: | Text |
| Language: | English |
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1989
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.1071.3896 http://www.kevinmbailey.com/uploads/3/0/5/8/3058136/bailey_1989.pdf |
| Summary: | ABSTRACT: In autumn 1984 the interaction of vertical migration of age-0 walleye pollock Theragra chalcogramma m the eastern Bering Sea, and cannibalism was examined. Patterns of verhcal migration were Inferred from acoushc observations, midwater trawls, and occurrence of juveniles in the stonlachs of adults caught in bottom trawls. Generally, most age-0 pollock were distnbuted in the near-surface layer at night. Dunng the day larger individuals moved through the thermocline into the bottom layer. Vanations in rmgratory patterns were observed and are discussed in relation to the thermocline, zooplanktan abundance, growth, and size. Age-0 juveniles from 50 to 60 mm ate n~ostly large copepods. At 3 stations the growth of juveniles, as inferred from otohth increment widths for the 10 d prior to capture, increased with zooplankton abundance. Of 1503 adult pollock stomachs, 29 contained juvenile pollock, all of which were age-0 fish, 20 to 100 mm in length. Adult pollock contained an average of 3.0 juveniles per stomach. The size composihon of juveniles in adult stomachs and the diurnal pattern of adult pollock feeding on juveniles indicated that cannibalism occurred mostly in daytime and was closely coupled with verhcal distribution patterns of juveniles. |
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