Recruitment forecasting model of the Japanese Pacific walleye pollock Theragra chalcogramma, incorporating the ocean environmental factors

This study analyzed recruitment fluctuation in the Pacific stock of walleye pollock Theragra chalcogramma. Here, we present a recruitment forecasting model that includes ocean environmental factors. We used the water temperatures in the Funka Bay as the independent variables. We tested whether the fluctuations in recruitment and spawning stock biomass could be reproduced using this model. Further, we investigated the effects on abundance and catch when the age of first capture was increased and the fishing mortality coefficient (F) was reduced. Fluctuations in recruitment and spawning stock biomass in the model reproduced the fluctuations observed in the data, indicating that fluctuations in recruitment can be reproduced by manipulating only the spawning stock biomass and water temperatures in the Funka Bay. The density-dependent effect is not necessarily required to explain the fluctuations. Increasing the age of the first capture and reducing F was necessary and the resultant effects were compensational.