The National Institute of Aquatic Resources monitored the movement and development of bluefin tuna in Skagen, Denmark on August 23.

The researchers equipped the tuna with transmitters that make it possible to map the fish's movements. Once the scientists put equipment on the fish, they were put back into the sea off the country's coast.

In 2017, four tuna were tagged, and by 2020, the number of tagged tuna had grown to 116.

Bluefin tuna previously roamed in Danish waters, but disappeared in the 1960s without scientists knowing the cause, according to Nord News. In recent years, they have returned, and now the researchers are trying to find out why the tuna are apparently thriving again at Danish latitudes.

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