BLUEFIN TUNA MIGRATORY BEHAVIOR IN THE WESTERN AND CENTRAL MEDITERRANEAN SEA REVEALED BY ELECTRONIC TAGS

SUMMARY During 2008 and 2009 several tagging expeditions were carried out in the Mediterranean in order to determine Atlantic bluefin tuna trajectories and behavior. Tagging activities during 2008 were concentrated in the western Mediterranean. In 2009 the Adriatic Sea area, where tagging with pop-up tags on wild tuna had never taken place before, was also covered. Pop-up satellite archival tags and internal archival tags were used for adults and juveniles respectively. In total 4 pop-up and 21 archival tags were deployed in 2008, while 11 pop-up and 2 archival tags were used in 2009. Tagged bluefin tuna weights ranged from 12 to 200 kg. Data from all pop-up tags was successfully recovered and their retention rates ranged from 1 to 172 days. Additionally, a 2008 archival tag was recovered after 391 days at liberty. None of the tagged tunas left the Mediterranean Sea during the whole tracking period. Results suggest a residence pattern for large adults north of the Balearic Islands in late summer, and a link between the Gulf of Lions and the Tyrrhenian Sea, and between the Adriatic Sea and the Libyan coast. RESUME