Simulating harvest strategy trade-offs for tuna fisheries in the Western and Central Pacific Ocean

The Western and Central Pacific Ocean (WCPO) is home to the world’s most productive tuna fisheries. The responsible regional fisheries management organization, the Western and Central Pacific Fisheries Commission (WCPFC), is increasingly adopting harvest strategies to support sustainable exploitation of key stocks. In this study, we assess the ecological, economic, and social implications of three harvest strategy scenarios of interest to WCPO stakeholders: (1) rebuilding juvenile tuna stocks via reduced fisheries mortality, (2) sustaining baitfish populations used by pole & line fleets, and (3) improving bigeye ( Thunnus obesus ) and yellowfin tuna ( Thunnus albacares ) stock status. Using a scenario-based bioeconomic modelling framework, we simulated the catches of skipjack ( Katsuwonus pelamis ), yellowfin, and bigeye tunas across multiple fleets – including longline, purse seine and small-scale fisheries – with a focus on Indonesia, the Philippines, and Vietnam, alongside broader WCPO fleets. Our results suggest that, over the long term, all three harvest strategies can generate both ecological gains and net economic benefits. However, outcomes varied markedly among fleets within each country, with purse seine fleets experiencing the greatest simulated economic losses. Despite this, when aggregated across domestic fleets, total estimated economic benefits increased for all three focal countries under all three scenarios. This study offers a foundational modelling framework for exploring proposed tuna harvest strategies and highlights how conservation burdens in an international fishery may be more equitably addressed through domestic-level management considerations.