Weight-based yield per recruitment and spawning-biomass per recruitment analyses of pacific cod Gadus macrocephalus off the Pacific coast of southern Hokkaido,Japan

ABSTRACT:   The present study assessed the stock state of Pacific cod Gadus macrocephalus caught off the coast of southern Hokkaido, Japan. Weight-based yield per recruitment (YPR) and spawning-biomass per recruitment (SPR) analyses were used for this assessment. The current fishing mortality (average from 1998 to 2000) was 0.65 and weight at first capture was 0.5 kg bodyweight. Under these fishing pressures, the YPR of Pacific cod in southern Hokkaido was 1.06 kg/recruitment and percentage of SPR (%SPR) was 6.9%. The %SPR was lower than the critical limit at 20%SPR. The main reason that values of both YPR and %SPR were not optimum, would be that the weight at first capture was too small. Raising the weight at first capture was thought to be a better strategy from the biological viewpoint, and reducing fishing mortality to 0.3 would be the next alternative strategy from the fisheries management viewpoint.