Trans‐Basin Climate Events Modify Distribution and Catchability of Large and Small Size Classes of Bigeye Tuna ( Thunnus obesus ) in the Indian Ocean

ABSTRACT The sustainability of global tuna fisheries exhibits regional divergence, with some stocks showing significant recovery while Indian Ocean bigeye tuna ( Thunnus obesus ) remains overfished. Particularly against the backdrop of intensifying global climate change, both large and small size classes of bigeye tuna are experiencing shifts in distribution and catch rate patterns influenced by trans‐basin climate events. This study focuses on the effects of trans‐basin climate change on the resource dynamics of bigeye tuna in the Indian Ocean, comprehensively considering the differing responses of large and small size classes to environmental changes. We systematically examined the causal relationship between trans‐basin climate events and tuna resource fluctuations by integrating fishery and climate data using the Convergent Cross‐Mapping (CCM) method. Concurrently, the Climate Events Synergy Model (CESM) was employed to analyze the interactions between these climate factors and the Indian Ocean Dipole (IOD) in shaping tuna habitat suitability. Results indicate that different trans‐basin climate events exert heterogeneous impacts on large and small size classes of bigeye tuna by altering water temperature, nutrient transport, and circulation patterns, and these events affect the resource dynamics in conjunction with the IOD. This study provides scientific evidence for elucidating the mechanisms underlying tuna resource fluctuations under multi‐scale climate drivers in the Indian Ocean, holding significant implications for formulating climate‐specific fisheries management strategies and addressing climate change challenges.