The state of the walleye pollock in the northern part of the Okhotsk Sea, North Pacific

Abstract

Aspects of pollock biology, including growth and mortality rates are presented, based on 4 years (1991–1994) sampling of Polish commercial catches in the international waters of the Okhotsk Sea. To estimate stock dynamics, production models were fitted using Russian CPUE data, 1985–1993. The length of fish in the catches ranged from 23 to 65 cm, with a dominant mode of 35–45 cm. Fish aged 2–22 years were recorded, with fish 4–8 years old dominating the catch. The mean age and length of the exploited fish were stable in the period analyzed. The von Bertalanffy's growth curves fitted to males and females separately showed a significantly higher asymptotic length for females. Specimens with gonads at the spawning stage were found in the catches, suggesting that the spawning ground is nearby. Biomass estimates for the most recent years were about 10 million tons, and mean fishing mortality was 0.19. The natural mortality value obtained by the Pauly (1980) formula was 0.2. The optimum catch levels, resulting from production models, slightly exceed 2 million tons, and the optimum fishing mortalities are in the range 0.27–0.30. This is consistent with the F − 0.1 value from the yield per recruit analysis.