New Fishing Strategies to Face Climate Change Effects on the Spanish Tropical Tuna Fisheries Off Indian Ocean

Tropical tunas, including yellowfin (Thunnus albacares), are recognized as a crucial contributor to global food security. Moreover, yellowfin tuna is the most commercially valuable tropical tuna. The Spanish purse seine freezer fleet, actively operating in the Indian Ocean, emerges as a leading contributor to the global yellowfin tuna catch. Currently, the planet is undergoing a climate change, which is poised to alter habitats on a global scale, particularly impacting tropical regions by causing an increase in sea surface temperatures at an unprecedented rate as well as ocean deoxygenation. Consequently, it is foreseeable that large pelagic highly migratory species like tunas may shift their distribution areas, resulting in the translocation of the current fishing grounds. In this context, the main goal of this work is to study the potential shifts of the Spanish purse seine fishing grounds targeting yellowfin tuna within the tropical belt in the Indian Ocean. Our findings suggest that although the largest yellowfin tuna catches have moved northward in latitude, most of the fishing effort, indicated by the greater number of fishing sets, has been located toward the equatorial region. Present results can only be interpreted from a human perspective and following a commercial strategy in response to the management of yellowfin tuna. Therefore, according to the 38 years of the analyzed dataset, a shift in fleet dynamics is apparent. However, we suggest that this new fishing strategy could be not so much attributed to the movement of free schools toward higher latitudes but to complex trade-off strategies.