Incentives for optimal management of age-structured fish populations

We characterize optimal fishery management in an age-structured, bio-economic model where two age groups are harvested with costly and imperfect selectivity. We show that a system of tradable fishing permits, each allowing to harvest a specific number of fish that differs with age group, implements optimal age-structured harvesting, while traditional biomass quotas fail to solve the problem of growth overfishing. With our system, gear restrictions (such as mesh-size prescriptions) become obsolete. We apply our model to the Eastern Baltic cod fishery and quantify the benefits of optimal age-structured management.