School of Atlantic bluefin tuna (Thunnus thynnus) swimming in the deep waters of the Atlantic Ocean.
Photo: Adobe Stock.
Live capture and storage of Atlantic bluefin tuna has been achieved for the first time by Norwegian researchers, in collaboration with local fishermen.
The team aboard fishing vessel Vestbris, aided by Directorate vessel Fjordgyn, captured one bluefin tuna off the Stad peninsula in northwestern Norway, an area known for its rough seas. The fish was then transferred to a specially-designed transport cage, and towed to shore.
One week later, the team built on this milestone, managing to trap and transport 22 live bluefin tuna, each weighing between 200 and 300 kilos.
The exploratory project, led by the Norwegian Directorate of Fisheries, aimed to assess the feasibility of capturing bluefin tuna for live storage in cages in Norwegian waters. The marine researchers had been trying to achieve this feat for several years, with no success until this summer.
"We have learnt a lot by these small proofs of concept," said Institute of Marine Research (IMR) project manager Manu Sistiaga, in an IMR news announcement.
Already some of the initial catch was transferred to market in Oslo, while samples were retained for further investigation by Nofima and IMR researchers.
The technique for capturing and holding live tuna is currently used quite commonly in the Mediterranean, but has not yet been successfully implemented in the colder and wilder waters of the north Atlantic.
Norway is the northernmost border of the bluefin tuna's range, with the fish reaching Norwegian waters during their annual feeding migration. The bluefin tuna is the world's largest tuna species and, according to the Norwegian Directorate of Fisheries, it is only the largest individuals that make their way this far north.
The researchers commented that although Norwegian fishermen have access to tuna through the purse seine fishery, this creates problems as large catches cannot always be handled quickly enough to maintain high quality, and large amounts of fish come to market all at once, impacting prices.
The Norwegian authorities see live storage as a possible solution for such problems, but more work is needed, researchers say.
"In the long run, we need to find out how long the fish can be safely kept in a cage, what food they would need and what sea tempertures they will thrive in. But first we need to improve on the catch, transfer and transport," said Sistiaga.
International regulations on the practice of capturing live tuna may also pose a challenge in Norwegian waters, the team note.
The International Commission for the Conservation of Atlantic Tunas (ICCAT) oversees the regulatory framework, however, "The regulations are adapted to the fisheries in the Mediterranean, where the conditions are drastically different from here," says Hermann Pettersen, project manager at the Directorate. "They can use divers for many operations, which we cannot."
Earlier this year, Norway's portion of the international fishing quota for bluefin tuna was established at 383 tonnes. The species has been overfished in the past, but strict international regulations have allowed its numbers to increase in recent years.