Leveraging port state measures to combat illegal, unreported, and unregulated fishing

Illegal, unreported, and unregulated (IUU) fishing threatens the sustainability of fisheries and communities dependent on them. The Port State Measures Agreement (PSMA) is a key tool for combatting IUU fishing by foreign fleets, requiring standardized inspections, information sharing, and port denial. Using satellite data, we characterized how PSMA has affected high seas vessel behavior and identify opportunities to strengthen its impact. PSMA adoption has increased travel distances to the nearest ports in States not Party to PSMA and channeled more fishing effort to domestic and PSMA Party ports. However, domestic fishing fleets need greater attention because they constituted 66% of port visits in 2021. Among reflagged vessels, we also found a 30% increase in visits to PSMA ports by vessels shifting to domestic flags after PSMA entered into force, allowing them to avoid PSMA requirements for foreign vessels. Our results highlight the centrality of implementing consistent, effective port State measures across foreign and domestic fleets to address IUU fishing risks.