Cefas scientists have teamed up with the University of Exeter to map the distribution and movements of Atlantic bluefin tuna in UK waters. The sightings are coming in thick and fast as the tagging season gets underway.
The Atlantic bluefin tuna is an iconic fish species, whether your perspective is as a consumer, a fisher, or as a naturalist. They were once a common sight in UK waters and instigated the foundation of the world-renowned British Tunny Club, established in 1931 by a collection of aristocratic sport fishermen. At that time, keen anglers followed the herring boats out to sea with the allure of capturing giant bluefin tuna more than 250 cm in length and over 250 kg in weight; a regular occurrence in the North Sea at that time. However, catches dropped away in the 1960s and bluefin tuna all but disappeared from the North Sea, maybe never to return?
Bluefin tuna make a comeback
Since 2014, sightings of bluefin tuna have been rising annually, and this year is no exception. Reports of large shoals of tuna have been reported in the North Sea, the Celtic Sea and into the western English Channel. They are fast-swimming, powerful fish and voracious hunters; they often surge out of the water as they chase sardines or other pelagic fish prey. Tuna are frequently spotted in the company of other top predators, such as dolphins and diving seabirds. Because of this, tuna sightings are now logged routinely by wildlife watchers, through scientific surveys, or simply through reports or videos posted on social media.
Photo credit: Tom Horton
Hannah and Duncan Jones of Marine Discovery Penzance, a local wildlife tour operator, said “We've already seen bluefin tuna on 45 occasions this year and our season isn’t over yet. Most of those instances have been large shoals with a mix in the size of fish but recently most fish seen at the surface have been large. We have certainly seen more this year than ever, which has been the case every year now since 2015!”
Sightings from the October Cefas PELTIC survey in the Celtic Sea have numbered more than 30 shoals of tuna in the last 4 years and mentions on Twitter of bluefin tuna sightings in the southwest UK has risen considerably since 2012.
Why are bluefin tuna back in UK waters?
Getting a better idea of why bluefin are back, and what they do during their residence in UK waters is the purpose of the Thunnus UK project, a collaboration between Cefas and the University of Exeter, funded by Defra and the European Maritime and Fisheries Fund. David Righton, who leads the project at Cefas, said: “our job is to find out as much as we can about why bluefin are in our waters. Over the next two years, we’ll be compiling sightings and mapping their migrations using satellite-communicating electronic tags”.
Photo credit: Tom Horton
Matthew Witt, the project lead for Exeter, agrees: "We’ve already learned a huge amount about bluefin from talking to wildlife spotters and fishers who are out on the water every day. Our tagging programme will help build an even more detailed understanding at the level of individual fish”.
Tagging started in October, and the programme has been designed with the input and help of fishers. Cefas and Exeter are halfway through the 2018 tagging programme and have been working with Fred Smith, skipper-owner. Fred said: “Bluefin tuna have been seen here in great numbers again this year, and it’s great to be part of the efforts to find out more about them. I’m looking forward to seeing what these tags can tell us!”.
An exciting time for bluefin tuna spotters lies ahead.
Note: The UK does not have a quota for bluefin tuna and targeting or landing bluefin is strictly prohibited https://marinedevelopments.blog.gov.uk/2017/09/04/bluefin-tuna-in-uk-waters/ . Should a bluefin be caught accidentally, guidelines are available for returning it to the sea in the best possible health https://www.thunnusuk.org/aim-3-advice-for-fishers