Weight-based virtual population analysis of Pacific cod Gadus macrocephalus off the Pacific coast of southern Hokkaido, Japan

ABSTRACT:   Age-based population assessment is widely used, but there are cases where information on age or even body length of landed fish is difficult to collect. In the present study, the biomass and fishing mortality of the southern Hokkaido stock of Pacific cod Gadus macrocephalus was estimated directly from body weight composition, using weight-based virtual population analysis, from 1994 to 2000. The estimated biomass over 1 kg body weight was 5607 t in 1994 and increased to 7908 t in 2000. The increase was explained by an increase in recruitment.