It’s Bluefin season in the UK, and there’s something special about seeing the giants burst out of the water just off the coast of Falmouth, and not only because until a few years ago, they had seemingly been absent from British waters.
Atlantic Bluefin tuna have been known to grow to an incredible 700kg (1,500lbs) – the equivalent in weight to a black rhino or three adult male lions – swim up to 45 miles per hour, and dive to depths deeper than 1800 metres. Thanks to being unusually warm-blooded, they are one of the only fish that can travel from the balmy 33C seas of the equator to the extremely fresh 6C waters of the Arctic Circle.
“To have something that big and impressive in our water is exciting. There’s just so many things about them that excels,” says Dr Lucy Hawkes, associate professor of biosciences at the University of Exeter. “Their physiology has evolved to make them excellent top predators, including retractable fins so they can nip, turn and zoom through the water.”
It’s little wonder they’re admired by scientists for their incredible biology, prized by anglers for the challenge of the catch, and coveted by chefs for their buttery belly meat – a once sushi bar novelty now finding its way onto fine-dining menus across the globe.
At London’s first conveyor belt sushi restaurant, Moshi Moshi, a special seven-course Bluefin tuna tasting menu will be held next month, featuring maguro (lean tuna) and toro (fatty belly) sashimi, alongside smoky tsukune (grilled tuna meatballs). Despite Bluefin being a sushi favourite, it will be only the fifth time it has appeared on the Japanese restaurant’s menu in 28 years. [Link to substack for more on this story?]
“To have it on our menu is amazing and to have it coming from British waters is even better,” says founder, Caroline Bennett.
Conservation success story
Although the decision cost Bennett a lot of customers, she stopped serving Bluefin at Moshi Moshi in 1998, after learning that perverse incentives to catch and fatten the fish had caused their populations to crash catastrophically in the 1990s.
Thanks to campaigns by the likes of Greenpeace, Atlantic Bluefin tuna had become a figurehead for the fishing industry’s mismanagement and greed. Emergency efforts to protect the endangered species have had to be coordinated across nations as Bluefin can travel from Nova Scotia to the Mediterranean.
As such, fishing bans and quotas are led by ICCAT (International Commission for the Conservation of Atlantic Tunas) and supported by international agreements. Though the measures have not been without their shortcomings, the eastern Atlantic and Mediterranean stock is believed to have made a substantial recovery. Yet, we still don’t know exactly how many there are.
The return of Bluefin to British waters is one of the signs of a recovering stock. Fishers and eco-tour operators started reporting seeing ‘funny-looking dolphins, with their tails on the wrong way’ off the coast of Cornwall around 2014. The team at the University of Exeter soon realised they were Atlantic Bluefin tuna and secured EU funding to research further. “We would usually have to travel the world to study marine vertebrates of this calibre, but suddenly we had them on our doorstep,” says Hawkes.
Fast forward to 2026 and the catch of record-breaking sized Bluefins weighing 300kg off Whitby and Scarborough are making national headlines. Bluefin fishing here was famous in the 1920s and 1930s, attracting Hollywood celebrities such as Clark Gable and Errol Flynn, but the last reports of the giant fish being landed in the North Sea were in the 1960s.
“That’s where we’ve spent this summer – in the North Sea working with some of those eye-wateringly massive beasts,” says Hawkes. “The biggest one we caught was 9ft 7”, it’s an astonishingly sized fish. It took five of us to pull it up on the boat and my back actually still hurts a little bit now.”
Bluefin migration patterns revealed
The team and CEFAS (Centre for Environment, Fisheries and Aquaculture Science) have been working with anglers to catch, tag, and release Bluefin tuna since 2018 to learn more about their migratory patterns, as part of an international effort coordinated by ICCAT. Around 3,000 fish have been tagged in the UK so far, so they can be identified if they turn up anywhere in the world.
Around 170 Bluefin were also fitted with electronic tags, which record the fish’s location, depth, the temperature of the surrounding water and its acceleration every 15 seconds. At a cost of about £5,000 per tag this was a necessarily more limited study, but continues to provide incredibly detailed insights into their behaviour and migratory patterns.
We now know The Bay of Biscay is their winter location of choice; every Bluefin that was tagged in the English Channel ends up there by January. Come late spring or early summer, some move into the Mediterranean, typically to spawn, spreading all the way from the Balearics to Türkiye. Others swim half way across to the Atlantic – why, we are yet to find out. Then they all seem to reconvene in the Channel from around August until December, perhaps following food and feasting on oily fish such as mackerel, herring and squid. A few will then go up the coast of Ireland and start looking at Scotland, but none of the tuna tagged in the Channel have ever gone into the North Sea. “Which is really interesting. We know there are Bluefin there, so why not these ones?” asks Hawkes, highlighting another mystery that needs solving.
The data has uncovered other secrets of the sea, too. One electronic tag, for example, washed up on a beach in France. When the team extracted the data, they discovered the tag had become lodged in the stomach lining of an Orca that had eaten the tuna. The tag had remained there for 11 days before, the team believe, the whale vomited it up. “So we now accidentally have the world’s longest killer whale track,” says Hawkes. “Incredibly, the tag shows the killer whale hunting, chasing, and catching the tuna. You can even see the tuna getting flipped belly up and thrown out of the water. It’s all there in the data.”
Ranching as a threat
Aside from killer whales, their main predator is humans.
Two of the tagged tunas got caught up in Bluefin ranching operations in Türkiye. Tuna ranching – capturing live tuna and fattening them up in cages – is big business in the Mediterranean, especially in Malta, Spain, and Türkiye. Fishing is a notoriously murky business and a lack of reliable data is obscuring the true scale of the industry’s expansion. However, the FAO (Food and Agriculture Organisation of the United Nations) reports that total aquaculture production – not just Atlantic Bluefin – is on the rise in Mediterranean and Black Sea countries, reaching 2.97 million tonnes of fish in 2023, worth almost £8 billion – a growth that brings its own impacts on marine ecosystems.
We also know the reported number of tuna scooped up in purse seine nets – essentially giant drawstring bags – have now almost reached the historic highs of the 1990s, with around 99% of purse seine-caught tuna in the Mediterranean transferred to farms for fattening, according to the latest research by Compassion in World Farming.
Their latest report, Atlantic Bluefin Tuna: Caught, Caged, and Under Threat, reveals that in 2003 around 55,000 tuna were ranched per year; in 2024, farms were ranching around one million tuna.
“This is only the reported catch,” caveats Dr Elena Lara, who compiled the report. “Official data sets do not match and there’s historic reports of illegal fishing and quotas not being respected.” Illegal, unreported and unregulated fishing (IUU) is taken into account when deciding international fishing quotas, but there’s still uncertainty over whether the actual number being caught is within sustainable limits for the species.
This is particularly concerning, as ICCAT’s current management approach assumes that Atlantic Bluefin tuna begin spawning at around five years old. But Hawkes highlights that their latest research suggests Bluefin may not start reproducing until they are eight- or nine-years-old. If that’s the case, catching them before they’ve had a chance to spawn could have serious consequences for the future of the species.
Dr Lara concludes: “If this pattern of exploitation continues then we might see the species struggling again. Of course, this doesn’t only impact the Bluefin in the Mediterranean, it will impact the numbers that arrive in the UK too.”
The future of the species
Hawkes confirms that we currently don’t know how many Bluefin are in UK waters; it could be anything from thousands to tens of thousands. Yet, the UK’s fishing quota has increased sharply, from 63 tonnes in 2025 to 230.56 tonnes for 2026–28. That sounds like a lot, but it still represents less than 0.5% of the 48,403-tonne total allowable catch for Bluefin in the eastern Atlantic and Mediterranean.
This year, 120 tonnes is being used for a commercial fishery, with up to 30 small vessels each allocated four tonnes, while a further 20 tonnes is for recreational catch-and-release fishing, including for incidental mortality. Again, the system isn’t perfect, but fishing standards are fairly high – commercial boats must use rod and reel, and recreational skippers must complete mandatory training covering fish welfare and best-practice handling to give the tuna the best chance of surviving after the wrestle of the catch.
As an Associate Professor of Biosciences, Hawkes doesn’t fish for sport, but she received her first hate mail from animal activists a couple of weeks ago for talking positively about the angling industry. She acknowledges there are bad actors, but more commonly finds that “anglers are huge advocates for the fish, they love them and want to protect them.”
Thanks to her job, Hawkes chooses not to eat seafood herself either, but she isn’t opposed to the Bluefin culinary market developing in the UK. “If the meat really is of the most spectacular quality, then maybe we could have the most ethical, highest welfare, best tuna in the world that we still keep at a very limited supply.”
Her reasoning is the same: “I just want Bluefin to stay special.”
Bennett also believes that Bluefin should be revered. She maintains that Bluefin will never again become a staple for Moshi Moshi, only ordered from British fishers and served seasonally as a rare treat.
One thing is certain: Bluefin are back in bigger numbers in British waters. The question now is whether we can learn to value and respect them – or whether human behaviour will once again put them at risk.
Read the full article by Lizzie Rivera here.
Photo of Bluefin Tuna breaching in Torbay, Devon, UK, taken by Ray Harrington on Unsplash
Lizzie Rivera is the founder and chief purpose officer at Live Frankly. Alongside her work for Wicked Leeks, she has been writing for mainstream publications for 10 years, specialising in sustainability and ethics since 2014.
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