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Cohort Dynamics of Walleye Pollock in Shelikof Strait, Gulf of Alaska, during the Egg and Larval Periods
Author(s) -
Kim Suam,
Gunderson Donald R.
Publication year - 1989
Publication title -
transactions of the american fisheries society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.696
H-Index - 86
eISSN - 1548-8659
pISSN - 0002-8487
DOI - 10.1577/1548-8659(1989)118<0264:cdowpi>2.3.co;2
Subject(s) - pollock , biology , fishery , larva , abundance (ecology) , juvenile , ichthyoplankton , biomass (ecology) , population , gadidae , zoology , ecology , fish <actinopterygii> , demography , atlantic cod , sociology , gadus
We estimated population parameters for early life stages of walleye pollock Theragra chalcogramma from 1981 ichthyoplankton samples collected in Shelikof Strait, Alaska. Instantaneous mortality of eggs was high before peak spawning (about 0.40/d) and decreased to about 0.10/d toward the end of the spawning season. This change can be explained in part by decreasing numbers of cannibalistic juvenile and adult walleye pollock in the spawning area. The mortality of larvae 4–10‐mm in standard length was generally less (about 0.09/d) than that of eggs. Total egg production estimates from egg sampling and hydroacoustic surveys of adults were 6.62 × 10 14 and 7.17 × 10 14 , respectively. Egg surveys resulted in good agreement with other methods for estimating walleye pollock biomass. Total spawner biomass estimated by the egg production method was 3.1 million tonnes, which was not substantially different from the hydroacoustic (3.4 million tonnes) or cohort analysis (2.4 million tonnes) estimates. Simulated larval abundance over time, based on daily egg production and egg and larval mortality, showed good agreement with observed larval abundance. The predicted values for total abundance of larvae in late April and late May were 18.93 × 10 12 and 4.21 × 10 12 , respectively, whereas observed values were 18.79 × 10 12 and 4.15 × 10 12 .