Researchers are studying the reappearance of Atlantic bluefin tuna off Scotland, a species that was once common around the British Isles before disappearing in the 1990s. In recent years, tuna have been frequently sighted from late summer to winter.
The Western Isles, where the first recorded rod-line catch of an Atlantic bluefin tuna was made in 2013, is a focus of the research. The fish caught six years ago by Angus Campbell, an Isle of Harris-based boat operator, weighed 515lb (233kg).
Scientists are collaborating with Mr Campbell and experienced anglers to catch, tag and release bluefin tuna back into the sea. Previously, tuna tagged off the remote Scottish archipelago of St Kilda were tracked to the Azores and the Bay of Biscay.
The latest research is being carried out by Thunnus UK, a collaborative project involving the University of Exeter, the Centre for Environment, Fisheries and Aquaculture Science (Cefas), and the Tuna Research and Conservation Centre of Stanford University.
Scientist Tom Horton said little was known about why bluefin tuna had returned to British waters. He told BBC Scotland: "We are seeing Atlantic bluefin tuna coming back to the British Isles after a period of quite a long absence. The bottom line is we really know very little about this animal so we are here to try and figure out a little bit more."
Mr Campbell expressed hope that eventually enough bluefin tuna would return to Scottish waters for anglers to take catch-and-release trips.
