The recapture of a bigeye tuna (Thunnus obesus) tagged in 2016 is providing scientists with a unique opportunity to refine bigeye tune stock assessment models and strengthen the scientific basis for sustainable fisheries management.
The bigeye tuna was recently caught in the equatorial Atlantic by a Galician longliner. The fish was originally tagged off Cape Verde by an AZTI researcher as part of ICCAT’s Atlantic Ocean Tropical Tuna Tagging Programme (AOTTP).
The fishermen recognized the tag, retained the fish and notified ICCAT as well as researchers from AZTI and the Spanish Institute of Oceanography of the Spanish National Research Council (IEO-CSIC). Thanks to this collaboration between the fishing, scientific and management sectors, the specimen can now provide highly valuable biological information.
The analysis of this bigeye tuna is being carried out within the framework of the European project ITUNNES (Improving Tropical tUNa kNowledge for End userS), funded by the European Climate, Infrastructure and Environment Executive Agency (CINEA) and coordinated by AZTI under the European Maritime, Fisheries and Aquaculture Fund (EMFAF).
This exceptional recapture demonstrates how long-term scientific tagging programmes, combined with close cooperation across the fishing sector, research community and international organisations, continue to generate the robust evidence needed to ensure the sustainable management of tropical tuna fisheries.
The findings also reinforce the work carried out by theRegional Coordination Group on Large Pelagics in particular the work by the Intersessional Subgroup on Tropical Tunas, which brings together leading European scientific institutes to coordinate research priorities and strengthen the biological data available for tropical tuna stock assessments. Drawing on the experience of projects such as ITUNNES, the ISSG has recommended establishing a coordinated, low-intensity biological sampling programme under the next EU Data Collection Framework (DCF). The objective is to ensure the continuous collection of key biological information—such as age, growth and maturity—beyond the lifetime of individual research projects, in close coordination with ICCAT and partner countries. This long-term approach will help reduce scientific uncertainty and provide more robust evidence to support sustainable fisheries management.