Ecological characteristics of Walleye pollock eggs and larvae in the southeastern Bering Sea during the late 1970s |
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| Authors: | Kyung-Mi Jung Sukyung Kang Suam Kim Arthur W Kendall Jr |
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| Institution: | (1) E&C Technology Institute, Incheon, Kyunggi-Do, 405-839, Korea;(2) Salmon Research Center, National Fisheries Research and Development Institute, Yangyang, Gangwon-Do, 215-821, Korea;(3) Department of Marine Biology, Pukyong National University, Busan, 608-737, Korea;(4) AJALA Enterprises, 635 Wanapum Drive, La Conner, WA 98257, USA |
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| Abstract: | Walleye pollock (Theragra chalcogramma) is an ecologically and economically important groundfish in the eastern Bering Sea. Its population size fluctuates widely,
driving and being driven by changes in other components of the ecosystem. It is becoming apparent that dramatic shifts in
climate occur on a decadal scale, and these “regime shifts” strongly affect the biota. This paper examines quantitative collections
of planktonic eggs and larvae of pollock from the southeastern Bering Sea during 1976–1979. Mortality, advection, and growth
rates were estimated, and compared among the years encompassing the 1970s’ regime shift. These data indicate that pollock
spawning starts in late February over the basin north of Bogoslof Island. Over the shelf, most spawning occurs north of Unimak
Island near the 100 m isobath in early or mid April. Pollock eggs are advected to the northwest from the main spawning area
at 5–10 cm/sec. Larvae are found over the basin north of Bogoslof Island in April, and over the shelf between Unimak Island
and the Priblof Islands in May. Compared to 1977, the spawning period appeared to be later in 1976 (a cold year) and earlier
in 1978 (a warm year) in the study area. At the lower temperatures in 1976, egg duration would be longer and thus egg mortality
would operate over a longer period than in the other years. Mean larval growth appeared to be lower in 1976 than in 1977 and
1979. Estimated egg mortality rate in 1977 was 0.6 in April and 0.3 in early May. |
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| Keywords: | Pollock eggs pollock larvae southeastern Bering Sea regime shift larval growth |
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