Several years ago, I received a curious photo from a bass-fishing friend – let’s call him Andy. It was a bit blurred and, as I squinted to make sense of it, a second image flashed up. There was Andy, leaning over the edge of his boat and unhooking something so huge it couldn’t fit in the frame. I had questions, but had to wait until the evening when Andy was safely back on dry land to hear the answers.
He had motored out to a favourite bass mark off the south Cornish coast, he explained, then waited for the gulls to lead him to fish. Seabirds are drawn to a mass of small fish, such as whitebait, which are corralled into balls by larger mackerel and garfish. They in turn will be predated by bass – and a lure cast into the foaming morass of fish can often prove successful.
As Andy fished, so the splashes around him became ever more explosive. Just as he realised what was creating them, the rod thumped over and line began to stream from the reel. He was using a stronger set-up than normal; his usual choice of line would have snapped under the strain, but this one held – and the fish began to drag the boat sideways. Andy reckoned that he was towed for half a mile before the fish slowed down.
Then began an epic, Ernest Hemingway-esque two-hour tug of war. Somehow, the tackle held and he got the fish – a bluefin tuna – to the side of his boat, where he popped out the hook and watched it drift back down into the depths. “How big was it?” I asked. “Bigger than me,” Andy replied.
At the time, it would have been one of the first bluefin tuna taken on rod and line in British waters for many decades, but Andy felt compelled to keep it quiet. Aside from unwanted attention for him and the fish, there was a legal question. At the time, the Atlantic bluefin tuna (Thunnus thynnus) was classified as ‘endangered’ by the International Union for Conservation of Nature. It remains protected today though; thanks to a recent resurgence in its population, it was reclassified as of ‘least concern’ in 2021.
The revival of bluefin tuna in the North Atlantic is a tale that swims against the prevailing tide of marine ecology woe. Bad news is more frequently shared than good: we hear far more about the plight of hen harriers in England than about the continuing success of marsh harriers or ospreys, for example, and it often takes something spectacular to make a splash in the pool of negativity.
The bluefin tuna is certainly spectacular: an acrobat, a speedster and a true ocean giant. Andy estimated that the fish he’d hooked and released measured some two metres in length, and weighed well upwards of 100kg. And that would have been one of the smaller ones.
Bluefin tuna vs mackerel: what's the difference?
There are 15 species of tuna in the world, eight of them in the genus Thunnus, known as ‘true’ tunas. All species are part of the Scombridae family, which also includes the Atlantic mackerel (Scomber scombrus), a fish common in the waters around the UK.
Despite the disparity in size, there are clear similarities between mackerel and bluefin tuna: the sleek, streamlined shape, double dorsal fins and symmetrical tail that curves with the sharpness of a new moon. Both species also have rows of small, almost toothlike triangular finlets between the second dorsal fin and the tail, and relatively large, round eyes. Whereas mackerel grow to an average length of 30cm and a maximum of 60cm, though, adult bluefin tuna are huge – typically 2.5m long and weighing over 225kg, but can grow far larger.
What is the largest bluefin tuna ever?
The record bluefin tuna caught on rod and line in UK waters and ratified by the British Record Fish Committee weighed 386kg and measured almost 2.75m long. What may seem remarkable is that this fish was landed in 1933 by Lorenzo Mitchell-Henry off the coast of Whitby in North Yorkshire.
The North Sea might seem an unlikely location to find a tuna, but this was not an isolated capture. From 1930, and for a couple of decades afterwards, the Yorkshire coast became the epicentre of the tuna-fishing world. Special train services brought anglers to Whitby and Scarborough from London, some of them having already travelled thousands of miles. Hollywood legends such as Errol Flynn and John Wayne headed out on rowing boats, towed by larger yachts, in search of the vast herring shoals on which the tuna (then commonly known as tunny) would gorge.
The bluefin tuna is endothermic, meaning that it can warm some parts of its body – such as the eyes and brain – to temperatures higher than the water in which it swims. Its heart is able to tolerate drops in temperature, too, receiving oxygenated blood directly from the gills, allowing the tuna to swim at considerable depth and survive in cold water.
The tunny of the North Sea vanished in the 1950s, victims of overfishing – not only of themselves but also of their primary food source, the herring. Research suggests that the North Sea spawning-stock biomass of herring crashed by as much as 95% between the mid-1960s and late 1970s.
Dramatic decline of bluefin tuna
Through the second half of the 20th century, numbers of Atlantic bluefin tuna fell in similarly dramatic fashion. Research by the International Commission for the Conservation of Atlantic Tunas found that populations had fallen by 72% in the eastern Atlantic and 82% in the western Atlantic in the 40 years to 2009. A return of the tunny to UK waters seemed almost fantastical; rather, it was feared that Atlantic bluefin tuna might vanish altogether.
Humans are learning to address such problems, though. Sustainability has become more than just a buzzword, and international collaboration has enabled the implementation of catch quotas that can be monitored and adjusted.
The subsequent rise in tuna numbers suggests that overfishing was a driver of the original decline, but a predator is only ever as successful as its prey. Adult bluefin typically feed on smaller fish species such as sardine, mackerel, garfish and herring. They hunt in shoals, using speed and agility to panic smaller fish into bait balls, which they can then plunder.
Why are bluefin tuna so fast?
A bluefin has grooves along its back enabling its dorsal fins to fold and flatten flush to its form. Propulsion is generated almost entirely by the tail in a pattern known as thunniform motion. The head and body remains rigid, maintaining a torpedo-like form that slices through the water, reaching speeds of up to 45mph in short bursts. A bluefin often approaches quarry from below, exploding through the surface as it snatches its prey.
Bluefin are acrobatic, often leaping clear of the water, and can be mistaken for dolphins from a distance. Though dolphins are perhaps more likely to be simply playing, both animals may be using such aerial stunts as methods of communication and to dislodge parasites. The whitewater created will also confuse prey fish and aerial scavengers. The opportunistic gulls for which Andy watches while bass-fishing are reliant on sight to grab any fish injured or part-discarded during the feeding frenzy.
Impact of fishing
Unsurprisingly, given the bluefin’s size, speed and power, the species has long been a prized catch for game fishers. This is a true ocean giant, held in similar esteem to marlin, swordfish and tarpon. It’s also unsurprising that it was fishers – commercial and recreational – who first began to spot the bluefin’s recent return to the seas surrounding the British Isles.
Initially, bluefins were most commonly spotted off the west coast of Ireland, particularly by the crew of pelagic trawlers. Then, from 2010, numbers began to increase inshore. Within a couple of years, whispers of the return of bluefin to the Cornish coast were getting louder. Within a year of Andy’s encounter, those whispers had become a shout.
Commercial interest was inevitable. The bluefin tuna is highly prized as a food fish, and even a single individual can command a huge price. In January this year, a Pacific bluefin weighing just over 270kg sold at auction in Tokyo for US$1.3million (nearly £1m). For a skipper working a boat from a Cornish harbour, the return of the bluefin offers more than just an opportunity – a catch could be life-changing.
Conserving the bluefin tuna
Conservation was key to the species’ resurgence but, while the potential impact of fishing was being determined, recreational anglers were able to assist with the science. Tuna larger than the 1933 British record have likely been caught, but their sizes were only estimated. This is a pattern familiar across modern sea angling: the conservation of individual fish is more important than personal milestones. All tuna caught are tagged and released, and the subsequent tracking provides fascinating details of their movements.
Thunnus UK – a collaboration between the University of Exeter, the Centre for Environment, Fisheries and Aquaculture Science, and Stanford University in the US – found that bluefin travel from the open Atlantic and the Azores to suspected spawning areas in the Mediterranean Sea. They then head north in late summer, when some arrive in UK waters – normally from mid-August – with numbers building into the autumn.
In 2024, bluefin were spotted around the British coast at locations ranging from Kent at the eastern end of the English Channel, all the way up the western shore as far north as the Hebrides. Tunny may not have found their way back to Whitby and Scarborough yet but, given the current dynamic, it seems only a matter of time.
Where can you see bluefin tuna?
For now, the south coasts of Devon and Cornwall offer the best chances of seeing bluefin tuna from boats and dry land. Falmouth is a reliable place for sightings, where tuna may come in close – sometimes only yards from the shore. Gulls and other seabirds often augur an encounter, as Andy discovered. Keep an eye out for excited, and often noisy, winged gatherings: the water beneath them might just erupt in a spray of white and a splinter of fins as a fish the size of a wardrobe breaches the brine.
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Top image: bluefin tuna. Credit: Getty
