Oceanographic preferences of yellowfin tuna (Thunnus albacares) in warm stratified oceans: A remote sensing approach

Yellowfin tuna (Thunnus albacares, Bonnaterre, 1788; YFT) face extensive exploitation pressure worldwide owing to the attractive economics of these fisheries. A better understanding of how oceanography influences the distribution of YFT (or highly migratory species more generally) will improve the ability for fisheries management policies to achieve conservation (e.g., maintain a stocks reproductive capacity), economic (e.g., maximize gross domestic product), and social (e.g., optimize successful fishing opportunities) objectives. Such ecosystembased linkages, when combined with real-time remote sensing data, provide the predictive framework for enhancing favourable fishing opportunities and limiting excessive harvest. We examined factors influencing YFT distribution and behaviour using pop-up satellite archival tags and remotely sensed oceanographic data from two regions in the northern Indian Ocean. Tagged individuals did not exhibit significant deep diving or diurnal behaviour, and preferred ambient temperatures of 26–30°C and 25–29°C in the Arabian Sea (AS) and the Bay of Bengal (BoB), respectively. In general, tagged YFT were found to be in waters with sea surface temperatures of 26–29°C, 60% of the time andwithin a sea surface height-anomaly of ±6 cm 70% of the time. YFT avoided moving below the relatively shallow oxycline depth, which is indicative of the stratified waters of the AS and the BoB. Low dissolved oxygen levels are likely a limiting factor for tuna movement given their high oxygen demand. The northern Indian Ocean provides an opportunity to study climate impacts on fish distribution and movement, and our findings provide a basis for understanding how habitat and migratory patterns may be altered under climate change