Atlantic bluefin tuna is a highly valuable resource, but it has been severely overexploited and remains threatened by overfishing and illegal trade. Its management is particularly complex because the Atlantic is home to two populations: the eastern population, which originates in the Mediterranean, and the western population, which originates in the western Atlantic. The latter is less abundant and requires a higher level of protection.
Although the two populations are genetically distinct, they are indistinguishable by appearance. In the Atlantic “mixing zone”, individuals from both populations are caught together and, until now, it had not been feasible to accurately determine what proportion of the catch came from each population. This lack of traceability limited stock assessment, the effectiveness of management measures and the ability to set quotas with the required level of precision.
AZTI coordinated an international consortium involving partners from Africa, Asia, the Americas and Europe to develop a pioneering genetic tool: a kind of genetic “birth certificate” that makes it possible to identify the natal origin of captured Atlantic bluefin tuna, regardless of where they are caught.
The tool was developed by analysing more than 600 larvae, juveniles and spawning adults collected from the main spawning grounds, a particularly challenging task given the difficulty of obtaining early-life-stage samples from this species. Tens of thousands of genetic markers distributed across the genome were identified, from which a panel of around one hundred markers was selected to determine natal origin.
The method was subsequently applied to 1,000 adult tuna caught in the Atlantic, allowing their origin — eastern or western — to be assigned accurately, cost-effectively and non-invasively.
Sectors: Fisheries and aquaculture sector
Research lines: Efficient, sustainable fisheries and aquaculture
Research sublines: Sustainable fishery management