Evaluating the Taxonomic Scope of Tuna Regional Fisheries Management Organizations to Identify Management Gaps and Spatial Priorities in the High Seas

Abstract

Tuna Regional Fisheries Management Organizations (tRFMOs) are tasked with protecting biodiversity and ecosystem-related species, yet industrial tuna fisheries in the high seas result in significant bycatch mortality. tRFMO species mandates and which species have conservation and management measures (CMMs) remain unclear, as does how Biodiversity Beyond National Jurisdiction (BBNJ) protections will “not undermine” tRFMO governance. This study defines species mandates and active management by tRFMOs and identifies candidate areas for high seas area-based management tools (ABMTs) under BBNJ. Results show gaps in management of small tuna species and weak protections for ecosystem-related species. Candidate areas identified for ABMT include regions of high species richness and fishing effort, often aligning with productive upwelling systems. These findings highlight opportunities to advance ecosystem-based fisheries management and provide a data-limited approach to identify potentially ecologically significant areas in the high seas.