Bioeconomic losses from overharvesting tuna

Abstract

Stochastic dynamic programming is used to model the world's largest fishery-tunas of the western and central Pacific-and to show that adopting a biomass target that maximizes the discounted economic profits (BMEY) from harvesting would result in larger stocks compared to de facto biological targets, and also lower catches relative to business as usual. This result is obtained for the three major tuna species, including skipjack tuna, which is not currently considered to be overfished biologically. Gains from larger tuna stocks are shown to exceed US$ 3 billion and increase the likelihood of stock rebuilding as some of these higher profits could be used to compensate fishers and countries for transitional losses to higher biomass levels. Adopting a dynamic BMEY target thus offers a potential "win-win"-better conservation outcomes with larger fish stocks and higher economic profits.