Effects of biological, economic and management factors on tuna and billfish stock status

Commercial tunas and billfishes (swordfish, marlins and sailfish) provide considerable catches and income in both developed and developing countries. These stocks vary in status from lightly exploited to rebuilding to severely depleted. Previous studies suggested that this variability could result from differences in life-history characteristics and economic incentives, but differences in exploitation histories and management measures also have a strong effect on current stock status. Although the status (biomass and fishing mortality rate) of major tuna and billfish stocks is well documented, the effect of these diverse factors on current stock status and the effect of management measures in rebuilding stocks have not been analysed at the global level. Here, we show that, particularly for tunas, stocks were more depleted if they had high commercial value, were long-lived species, had small pre-fishing biomass and were subject to intense fishing pressure for a long time. In addition, implementing and enforcing total allowable catches (TACs) had the strongest positive influence on rebuilding overfished tuna and billfish stocks. Other control rules such as minimum size regulations or seasonal closures were also important in reducing fishing pressure, but stocks under TAC implementations showed the fastest increase of biomass. Lessons learned from this study can be applied in managing large industrial fisheries around the world. In particular, tuna regional fisheries management organizations should consider the relative effectiveness of management measures observed in this study for rebuilding depleted large pelagic stocks.Fil: Pons, Malte. University of Washington; Estados UnidosFil: Branch, Trevor A.. University of Washington; Estados UnidosFil: Melnychuk, Michael C. University of Washington; Estados UnidosFil: Jensen, Olaf P. Rutgers University; Estados UnidosFil: Brodziac, Jan. Pacific Islands Fisheries Science Center; Estados UnidosFil: Fromentin, Jean M.. Ifremer, UMR MARBEC; FranciaFil: Harley, Shelton J.. Aquaculture and Marine Ecosystems Division; Nueva CaledoniaFil: Haynie, Alan C.. Alaska Fisheries Science Center; Estados UnidosFil: Kell, Laurie T.. International Commission for the Conservation of Atlantic Tuna; EspañaFil: Maunder, Mark N:. Inter-American Tropical Tuna Commission; Estados UnidosFil: Parma, Ana María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; ArgentinaFil: Restrepo, Victor R.. International Seafood Sustainability foundation; Estados UnidosFil: Sharma, Rishi. Indian Ocean Tuna Commission; SeychellesFil: Ahrens, Robert. University of Florida; Estados UnidosFil: Hilborn, Ray. University of Washington; Estados Unido