Climate-driven ocean warming and productivity may reshape the future of tropical tuna fisheries

Skipjack tuna (Katsuwonus pelamis) is a commercially and ecologically dominant pelagic species across tropical oceans whose distribution closely tracks oceanographic variability. Anticipating how climate-driven ocean change will reshape its distribution and fisheries potential is therefore critical for future tuna management. Here, we quantify relationships between skipjack tuna catch biomass and environmental variability across the Indian Ocean using long-term fisheries records from the Indian Ocean Tuna Commission spanning 2005-2019. Environmental drivers were derived from Copernicus MyOcean datasets, and generalized additive models (GAMs) with cross-validation were applied to identify the oceanographic predictors most strongly associated with catch variability. Sea surface temperature, salinity, mixed layer depth, sea surface height, chlorophyll-a concentration, and net primary productivity emerged as the dominant environmental controls shaping skipjack distribution. Climate projections under low (RCP2.6) and high (RCP8.5) emission scenarios indicate contrasting distributional responses by the end of the century. Moderate warming (~+1 °C) is projected to reduce relative catch biomass across parts of the basin, whereas stronger warming (~+3 °C) expands thermally favorable conditions within equatorial regions (5°S-10°N; 58°E-78°E) as the species’ preferred thermal niche (26-29 °C) broadens. Rather than a uniform decline in fishery potential, these projections reveal a nonlinear redistribution of skipjack tuna habitat and catch biomass linked to shifting oceanographic conditions and productivity gradients. Our results indicate that climate-driven ocean warming may reorganize the spatial structure of tropical tuna fisheries, potentially reshaping fishing grounds and catch opportunities across the basin. These findings highlight the importance of adaptive, climate-informed management strategies capable of responding to the dynamic redistribution of pelagic resources in a rapidly changing ocean.