The economic efficiency of a time–area closure to protect spawning bluefin tuna

Summary 1.  Spatial management measures, such as time–area closures, offer a widely advocated strategy for managing bycatch in fisheries and fisheries that impact particular life‐history stages, like spawning. The effectiveness of proposed management strategies can be evaluated across different policy dimensions of which we focus on one – maximising total profit. We examine whether a time–area closure presents an economically efficient means to manage bycatches of Atlantic bluefin tuna Thunnus thynnus on their spawning ground in the Gulf of Mexico by longline fishermen targeting yellowfin tuna T. albacares . 2.  We combine a behavioural representation of bluefin migration with population dynamic models for the two species and an economic representation of relevant fisheries and solve for optimal, equilibrial management strategies. 3.  The models predict the western Atlantic bluefin population is close to open access harvesting conditions, and that rebuilding the bluefin population would increase overall economic revenues from the fisheries by 460%, regardless of the specific actions taken in the Gulf. 4.  Time–area closures in the Gulf are predicted to be economically costly if there is little scope for recovery of the bluefin stock. However, the models predict such closures would offer limited economic benefits if there were a broader commitment to rebuild the bluefin population. 5.   Synthesis and applications. Technological advances and improvements in our understanding of the life history of these and other species make increasingly precise spatial effort control possible in many fisheries. The case study illustrates when such management measures would maximise fisheries profits while accounting for population dynamics and differences in mortality from different fisheries. However, the case study also highlights that the more elementary policy challenge of preventing overfishing has still often to be overcome.