10 Yellowfin Tuna Tagging II

Read the full report here: BPMS – DG Yellowfin Tagging Expedition II Report

Yellowfin tuna (Thunnus albacares) are currently ‘Overfished and Subject to Overfishing’ in the Indian Ocean with an urgent need to rebuild the stock. As a global conservation and management strategy, large Marine Protected Areas (MPAs) have been increasing in number and size. The British Indian Ocean Territory (BIOT) Marine Protected Area provides a unique opportunity to investigate the role of MPAs in the protection and management of commercially important pelagic fishes, such as yellowfin tuna. Building on the January 2019 yellowfin tuna tagging expedition that was hindered by unfavourable fishing weather, a team of four Bertarelli Programme in Marine Science researchers, returned to Diego Garcia in September 2019 to continue the work. The primary objectives of this second expedition were to:

1. Deploy mark recapture floy tags on yellowfin tuna within the Diego Garcia recreational fishery.

2. Deploy up to 10 satellite tags on yellowfin tuna, billfish or pelagic sharks (if encountered) to quantify off-shore movement behaviour.

3. Collect tissue samples for isotopic and DNA analyses to provide information on the trophic ecology and habitat use of species within BIOT and on the patterns of connectivity of elasmobranchs and teleosts regionally.

4. Collect environmental DNA samples from around Diego Garcia.

5. Offer training to the Environment Officer and other interested personnel in tagging methods and the taking and storing of DNA and isotope samples.

The expedition again demonstrated that the Morale, Welfare and Recreational (MWR) vessels are appropriate platforms for tagging activities.