Pasaia, November 5.– The Basque longliner Arlanpi, with its home port in Ondarroa, has been awarded in the shark category of the annual tag recovery draw by the International Commission for the Conservation of Atlantic Tunas (ICCAT), after reporting the recapture of a blue shark tagged by AZTI. This case demonstrates the utility of collaboration between crews and scientific teams: a recovered tag provides information on species movements and their interaction with fishing.
Through this draw, ICCAT encourages the participation of the fishing sector in data collection that contributes to scientific advice and the international management of marine resources. The initiative strengthens necessary collaboration to study species that move across vast ocean areas and whose monitoring requires combining observations from different fleets and research teams.
The blue shark (Prionace glauca) was a female measuring 150 centimeters in total length, tagged by AZTI on July 30, 2024, at the continental shelf edge off Hondarribia, as part of the Blueshark project. One month later, on August 31, 2024, it was recaptured off Bermeo. Reporting the recapture allowed for the connection of both locations and added new data to the study of its movements.
The scientific value of tagging is built by accumulating observations. Recapture dates and positions, along with data collected during tagging, help study which areas sharks use and how their distribution varies. When comparable measurements are available, they can also provide information on growth.
By combining these records with other biological and fisheries data, it is possible to advance in identifying areas and periods of greater interaction between sharks and the fishing fleet. This knowledge contributes to improving population assessments and guiding management measures adapted to the biology of the species and fishing activity.
For a species of interest to the longline fleet like the blue shark, having information about its movements allows for a better understanding of its presence in fishing grounds. Crew collaboration extends the research scope beyond scientific surveys and connects the sector's daily activity with the generation of useful knowledge for its management.
The Blueshark project studies the distribution and migration patterns of the blue shark and the smalleye smooth-hound in the Bay of Biscay, as well as their spatial and temporal overlap with the Basque fleet. Its objective is to identify interaction areas and generate knowledge to guide measures for reducing incidental catches and fishing mortality of these species.
To achieve this, AZTI combines its expertise in tagging programs with the analysis of biological and fisheries activity data. Continuous collaboration with the professional fleet and recreational fishermen allows for obtaining information under real fishing conditions and addressing relevant questions for both the sector and the bodies responsible for assessing and managing these resources.
This track record has already yielded pioneering results: in 2024, the recapture of an Atlantic bluefin tuna tagged by AZTI nearly a year earlier provided the first scientific evidence of this species' fidelity to the Bay of Biscay.
In the case of sharks, tracking has allowed for the recording of movements from the Bay of Biscay to other areas of the Atlantic, such as the Azores and Cabo Verde. It has also shown that some individuals remain in the gulf longer than expected. These results suggest the hypothesis that this area may play a role in the reproduction or nursery of some pelagic shark species, a possibility that requires further investigation.
Through these programs, AZTI contributes to ensuring that management decisions are based on a more solid understanding of the biology and movements of highly migratory species.
The Blueshark project is funded by the Basque Government and co-financed by the European Union through the European Maritime, Fisheries and Aquaculture Fund (EMFAF).
