Decadal changes in growth and recruitment of Pacific halibut (Hippoglossusstenolepis)

Since the climate regime shift of 1976-1977 in the North Pacific, the indiv idual growth of Pacific halibut (Hippoglossus stenolepis) has decreased dra matically in Alaska but not in British Columbia. Recruitment has increased dramatically in both areas. The decrease in age-specific vulnerability to c ommercial longline gear resulted in a persistent underestimation of incomin g recruitment by the age-structured assessment method (CAGEAN) that was use d to assess the stock. This problem has been corrected by adding temporal t rends in growth and fishery selectivity to the assessment model. The recent sustained high level of recruitment at high levels of spawning biomass has erased the previous appearance of strong density dependence in the stock-r ecruitment relationship and prompted a reduction in the target full-recruit ment harvest rate from 30-35 to 20-25%. The climate regime shift affected a number of other stocks of vertebrates and invertebrates in the North Pacif ic. While the general oceanographic changes have now been identified, the s pecific biological mechanisms responsible for the observed changes have not .