Managing growth-overfishing is more important than managing recruitment-overfishing

Avoiding overfishing and ensuring the sustainability of the resource base is of prime importance for fishery management. Current policies predominately rely on aggregate estimates of stock biomass to set total harvest quotas. Since many commercially exploited fish stocks consist of several age-classes, and since many fish grow considerably with age, there might be added-value in selectively harvesting the most valuable age-classes. Moreover, recruitment is often highly uncertain, so that the value of basing management decisions on the size of the spawning stock is not clear. We calibrate a detailed model on the North-East Arctic cod fishery, investigating whether a manager would act differently when the size of today’s spawning stock determines tomorrow’s recruitment or when there is no link between today’s stock and tomorrow’s recruitment. We find that the manager would choose very similar policies; namely to only target those fish that have reached their full growth potential. This suggests that, in many cases, we can avoid recruitment-overfishing by adequately managing growth-overfishing.