Multiple lines of evidence highlight the dire straits of yellowfin tuna in the Indian Ocean

Yellowfin tuna (Thunnus albacares) are highly valued pelagic fisheries target species. Regional fisheries management organizations (RFMOs) are the principal mechanism that manage yellowfin tuna fisheries. Determining changes in population abundances is crucial for effective conservation and management. We use multiple methods for monitoring biomass trends and evaluating the status of yellowfin tuna in each ocean basin and show how additional, multiple lines of evidence can enhance our understanding of the conservation and exploitation status of this species. Our analysis of regional biomass trajectories and Catch-MSY++ assessments corroborate the findings of the most recent RFMO stock assessments suggesting yellowfin tuna in the Indian Ocean are in critical condition, while the Eastern Pacific yellowfin tuna population shows the lowest levels of exploitation. These results are supported by fisheries-independent data from baited remote underwater video systems (BRUVS), showing that the Indian Ocean yellowfin tuna population is the least common, least abundant, and smallest across all oceans. Our findings support previous claims of systematic and widespread overfishing of yellowfin tuna in the Indian Ocean and thus confirm calls to reduce current fishing levels to ensure the long-term viability of the species. [Display omitted] •Multiple lines of evidence corroborate RFMO assessments enhancing our understanding of yellowfin tuna conservation and exploitation status.•CMSY++ assessments confirm that Indian Ocean yellowfin tuna are overfished and subject to overfishing.•IUCN classifies Indian Ocean yellowfin tuna as ‘Vulnerable’ and biomass trajectories estimate that its biomass has declined by ∼70% since 1950.•Ecological data from BRUVS indicate that Indian Ocean yellowfin tuna are the least common, least abundant, and smallest across all Oceans.•This approach opens up additional avenues to understanding the conservation status of other large pelagic species.