LESSONS FOR STOCK ASSESSMENT FROM THE NORTHERN COD COLLAPSE

Fisheries assessment scientists can learn at least three lessons from the collapse of the northern cod off Newfoundland: (1) assessment erro rs can contribute to overfishing through optimistic long-term forecast s leading to the build-up of overcapacity or through optimistic assess ments which lead to TACs being set higher than they should; (2) stock size overestimation is a major risk when commercial catch per effort i s used as an abundance trend index, so there is continued need to inve st in survey indices of abundance trend no matter what assessment meth odology is used; and (3) the risk of recruitment overfishing exists an d may be high even for very fecund species like cod. This implies that harvest rate targets should be lower than has often been assumed, esp ecially when stock size assessments are uncertain. In the end, the hig h cost of information for accurate stock assessment may call for an al ternative approach to management, involving regulation of exploitation rate via measures such as large-scale closures (refuges) that directl y restrict the proportion of fish available to harvest, Development of predictive models for such regulatory options is a major challenge fo r fisheries assessment science.