A 300-kilogram bluefin tuna is brought ashore near Denmark’s Læsø

A 300-kilogram bluefin tuna caught near the Danish island of Læsø did not survive a research tagging project and is now being stored in a cold room at the local fish industry.

DTU Aqua researchers tag bluefin tuna to map their movements through the seas. The fish are normally released after tagging, but this tuna died, according to TV2 Nord.

Bluefin tuna disappeared from Danish waters in the 1960s, probably because of overfishing. Sightings have increased each year since 2015 in the Øresund, Kattegat and Skagerrak, especially during August and September.

Brian MacKenzie, a professor at DTU Aqua, said better management and control of tuna fisheries and their prey were among the main reasons for the species’ return. Herring and mackerel, which bluefin tuna eat, have also become more plentiful.

Tuna fishing is generally prohibited in Danish waters. Since 2017, DTU Aqua has tagged tuna caught in the area to study their migration between Scandinavian waters and spawning grounds such as the Mediterranean. The late-summer project receives funding and authorization from the Ministry of Food and works with fishermen experienced in big-game fishing.

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Based on the figures and information I have worked with, improved fisheries management and control for both tuna and their prey are two of the most important reasons we are now seeing tuna again in Danish waters.