A tuna that washed up at Kimmeridge has prompted experts to believe the fish has returned to Dorset waters after decades away.

A 9ft-long adult bluefin tuna was discovered dead and reported to the Dorset Wildlife Trust.

Tuna have been regularly spotted from the shore and from boats off Cornwall and out in the Channel but the appearance of one along the Dorset coast is a lot rarer.

Peter Tinsley, from Dorset Wildlife Trust’s marine awareness team, said: “Bluefin tuna have been absent from UK waters for getting on for 70 years.

"In the early twentieth century they were common in the North Sea but disappeared in the mid-50s.

"Two possible reasons are suggested – one was the ever more efficient targeting of the immense shoals of herring and mackerel that would have attracted the tuna, the other links the disappearance to a long term (60-100 years) fluctuation in sea temperature in the North Atlantic.

“Whatever the reason, the return of these impressive fish in the south-west is reason to celebrate and spotting one is a real privilege, one I’ve yet to have. 

“Most of the sightings are further west than Dorset, but definitely keep watching – the ocean is a big place, but it’s all connected.”

Dorset Echo: Bluefin tuna may become a more common sight in Dorset watersBluefin tuna may become a more common sight in Dorset waters (Image: Julie Hatcher, Dorset Wildlife Trust)

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Bluefin tuna can reach around 10ft and can weigh up to 400kg. It is built for speed, swimming up to 43 miles per hour in pursuit of its prey. It is an apex predator and as an adult has no predators apart from man.

Mr Tinsley added: “They are fast and furious and can be seen in large groups, sometimes with dolphins, feeding on bait fish. They can be enormous – the UK rod-caught record is 386kg caught off Whitby in 1933, though larger ones have since been caught and released. That also makes them very valuable – a single fish could fetch thousands of pounds.” 

However, it is illegal for recreational anglers to target tuna and a new fishery has just been opened in the UK, but it is still very tightly controlled.

Dorset Wildlife Trust is encouraging anyone who spots a tuna to let them know. This can be done via telephone 01305 264620 or email enquiries@dorsetwildlifetrust.org.uk.