Archival and Pop-up Satellite Tagging of Atlantic Bluefin Tuna

Abstract

Pelagic fish have historically been a challenge to study because of their large size and highly migratory movements. Previous technological limitations have recently been overcome using archival and pop-off satellite tags, enabling studies of long-term movements, oceanographic preferences and behaviors. Archival tags record information on depth, ambient and internal temperatures, and light levels. Their major advantage lies in the extensive detail of this information and the ability to extract geolocation and oceanographic information in addition to biological data. We have deployed 279 archival tags in Atlantic bluefin tuna (Thunnus thynnus thynnus) in the western North Atlantic. To date, 40 of these have been reported as recaptured from both the western Atlantic and the Mediterranean Sea. Detailed records up to 3.6 years in length have been obtained demonstrating that Atlantic bluefin prefer the top 200 m of the water column and spend more than half their time in the upper 40 m. Atlantic bluefin maintain a high internal body temperature despite encountering a wide range of ambient temperatures (2–30°C). Patterns of feeding behavior have emerged providing data on how often and when fish feed at sea. Geolocation estimates for electronic tagged western Atlantic bluefin derived from archival and pop-up satellite archival tags indicate these bluefin show visitation and aggregation in New England, Carolina, the Gulf of Mexico as well as the Mediterranean. Pop-up satellite tags have been deployed on 120 west Atlantic bluefin tuna. Ninety percent of the pop-up tags scheduled to transmit have delivered data or position information on time. Both types of electronic tag data can be combined with oceanographic data to reveal a complete picture of how and where these fish forage in the pelagic realm.