Celebrity chefs keep returning to a four-letter in their glossy recipe books: tuna. Gordon Ramsay offers sesame-encrusted tuna with watercress salad; Nigella Lawson knocks ups a time-saving tuna, crab and avocado wrap. Rick Stein? That'll be chargrilled tuna with salsa verde.
None of these dishes would have been in a best-selling cookery collection in the early 1990s. Tuna has become one of the great, healthy convenience foods of the modern age: unusual and expensive enough to be a treat; new enough to be fashionable, and easy to cook.
For decades, we ate only the tinned stuff: it was one of the great store cupboard staples, sold in shrink-wrapped five-packs that languished on the shelf with the tinned tomatoes and pasta. Nowadays, it's a different story. Supermarkets began airlifting fresh tuna steaks into their chiller cabinets a decade ago, feeding the fashion for this once-plentiful fish.
Tinned tuna remains the workaday fish eaten by millions across the developed world, in lunchtime sandwiches, and tipped into our evening meals of pasta bake and fish pie. In Britain, it's the second most-eaten fish (salmon is number one). And we aren't alone in our phenomenal consumption. The Americans eat it voraciously too. In Italy, tonno is a common dish, as is atun for the Spanish and thon for the French. (In Germany, big-eye is grossaugenthun.)
Along with their interest in all seafood, the Japanese are particular admirers of the meaty predator of the seas; they most prize the bluefin tuna, which fetches £125 a kilo on Tokyo's fish markets.
But it's Japan's fondness for the rarest and most exquisite tuna that has triggered the first big food crisis of 2009. Overfishing has left the Atlantic bluefin on the brink of extinction, and it will be wiped out in just three years, according to WWF. Yet only last week the Anglo-American restaurant chain Nobu refused to take it off the menu (while the Japanese industrial giant Mitsubishi has admitted freezing bluefin for future sale).
As the row over the future of tuna becomes a simmering bouillabaise, Sienna Miller, Elle Macpherson, Jemima Khan and others have signed a letter to Nobu demanding they drop bluefin, hinting that they may boycott their favourite haunt. Last weekend, Pret a Manger disclosed that it had taken tuna from a different species, yellowfin, out of its sushi boxes.
Meanwhile, internet boards are buzzing with fish-eaters professing their shock and disgust, vowing they will never eat tuna again. How did we get here? Are those tins in our larders a guuilty manifestation of man's pillaging of the oceans?
Tuna-fishing is at least 2,000 years old in the Mediterranean, where in-shore fishermen caught the plentiful bluefin. The Phoenicians established fisheries using hand-lines and primitive nets. Aristotle mentioned bluefin in his History of Animals in 350 BC; Pliny the Elder recommended eating tuna to treat ulcers. For centuries, the coastal peoples of Spain and Italy have caught this most majestic of tunas, by channelling it into a mile-long nets laid parallel to the shore. In the final net, the Chamber of Death, they are bludgeoned or harpooned.
For most countries of the world, though, tuna fishing is a new, thoroughly modern, industrial business. Tuna are ocean-going fish, with big migrations. You need to go a long way to catch them. Tuna are not like cod, which once thronged the shallow North Sea, before they too were fished-out.
Bluefin were only available in the Med because the populations that lived in the Atlantic darted back through the Straits of Gibraltar to spawn. It is this breeding stock which is being caught in ever small numbers every year – and which has itself become part of the global tuna business; almost all bluefin are now flown to Tokyo. The species served up in Italian coastal resorts are more likely to be yellowfin or albacore, caught far away.
Japan likes to claim an affinity for bluefin. Nobu justified its refusal to drop bluefin by saying: "The consumption of this fish is a cultural institution in Japan and there is still an enormous demand for this delicacy at all our restaurants."
Admittedly the Japanese were hunting tuna miles from Japan in the 18th and 19th centuries, and expanded their fleets in the 1920s and 1930s. Tuna, though, was not a practical fish when caught so far away from the markets, until the development of deep-freeze facilities in the mid-20th century.
In their book Japan's Tuna Fishing Industry, Anthony Bergin and Marcus Haward write: "The history of tuna in Japan is a fairly recent phenomenon. In feudal times it was considered to be a very low quality fish in Japan, and the poor would not eat it. One reason for this may have been a risk of food poisoning, as tunas have high body temperatures and the warm flesh spoils easily. Before the Second World War, the fatty meaty of tuna (toro and oo-toro), now highly prized in Japan, was considered to be of very low value and often discarded."
After the end of the Second World War, Japanese trawlers moved to the Solomon Islands, Northern Australia and Indonesia. In the 1950s, they moved further into the Indian, Pacific and Atlantic Oceans to catch tuna.
Meanwhile, another great tuna industry sprang up in San Diego, California, when a sardine fisherman, Albert P Halfhill, decided to plug a seasonal sardine shortage with a local species, albacore, which was once considered a nuisance. Demand was swelled when protein-hungry US troops went to the battlefields of the First World War.
Today, tuna is a $5.5bn business, with processing and canning centres across the world, in places such as the Maldives and the Philippines. By weight, 5 per cent of the world's entire fish catch is tuna.
Landings, though, are falling. Tuna, like almost every other fish and fishery in the world, is struggling. Ninety per cent of the world's marine megafauna have been eaten. The global tuna fleet is out of control. It catches other species with abandon, and throws away all but the tuna destined for your tin, sandwich or sushi box. But surely, you might ask, not the tuna in my supermarket, in my store cupboard?
Fishing is afflicted by the "tragedy of the commons". The fish are there, wild and free, and valuable; you just need a boat. Because tuna roam the oceans outside the 200-mile limit for territorial waters, the fisheries are regulated by five Regional Fisheries Management Organisations. They have such acronyms as ICCAT (the International Commission for the Conservation of Atlantic Tunas) and IOTC (Indian Ocean Tuna Commission)
In 2007, WWF published a damning report on the failures of these to police the main commercial species of tuna: skipjack yellowfin, Atlantic bluefin, Southern bluefin, Pacific bluefin, big-eye and albacore.
As Tuna in Trouble revealed, most of these seven species are fully exploited (i.e. the maximum sustainable amount to allow for recovery of the species), or are endangered. WWF says tuna fisheries face "severe and alarming tuna stock declines... poor fisheries conservation and management strategies... high levels of high levels of illegal, unregulated and unreported fishing..."
All species of bluefin are in trouble. Organised crime in Italy is in charge of some of the Atlantic bluefin industry and, according to Charles Clover, author of a book on over-fishing which is the subject of a new film, The End of the Line, "sleazy ministers" end up working at ICCAT.
Most big-eye and some yellowfin are in trouble; albacore is fully exploited. The one bright spot is the skipjack, a member of the mackerel family. Unlike the slow-breeding tunas, skipjack is smaller and spectacularly fecund; the "chicken of the seas" is most likely to be the tuna in your tin.
What concerns marine scientists, campaigners and journalists is not just what happens to the tuna and the humans who rely on it for protein, but what tuna-fishing is doing to the rest of the marine environment. Tuna skippers are secretive, but for his book, Clover obtained the accounts of scientific observers on the by-catch; what is unintentionally caught by fishing boats.
A Russian scientist, EV Romanov, estimated what was caught by the tuna fleet in the western Indian Ocean between 1990 and 1995. The boats caught 215,000 to 285,000 tons of tuna and: 2,500 tons of shark, 1,700 tons of rainbow runners, 1,650 tones of dolphin fish, 1,200 tons of triggerfish, 270 tons of wahoo, 200 tons of billfish, 130 tons of mobula and manta rays, 80 tons of mackerel scad, 25 tons of barracuda, 160 tons of miscellaneous fish, and an unspecified number of whales and dolphins. All thrown back into the sea – dead.
Some populations, such as leatherback turtles, are being heavily damaged; pushed to the brink of extinction, even though they are not being hunted. Purse seine boats that drop giant drawstring nets in tuna areas, and "long-liners" which sink lines of up to 80km, hooked with bait, are the biggest by-catch culprits.
Conservationists say pole and line fishing, where boats drops bait into the sea and fishermen claw the tuna into the boat (avoiding other species), are "cleaner" methods.
In a report from Greenpeace last year, and still available online, retailers and canning companies were ranked in order of their tuna-fishing policies. Sainsbury, Co-op and Marks & Spencer came top; Princes and John West – most of whose was from purse seiners – came bottom.
Julian Metcalfe, co-founder of Pret a Manger, changed the company's policies after watching The End of the Line. "Being in the food business, I was ashamed I didn't know more about the plight of the big-eye, the yellowfin and the bluefin. The bycatch which is going on is criminal," he said yesterday. From now on, his company is insisting only on pole and line-caught skipjack.
Professor Callum Roberts is a marine scientist at York University and author of The Unnatural History of the Sea. So, is it OK to eat tuna, I ask him. "You might wonder whether it's ethical to eat this fish given its impact on other species," he says. "The leatherback turtle has declined by 90 per cent in the last two decades, and long-line fishing is largely responsible for that." Seabirds have been badly hit by the lack of tuna. The now-depleted tuna used to drive their prey to the surface when hunting. There are countless other examples."
He warns that tuna's problems are a worrying sign of what's happening out in the oceans. "The tuna are right at the top of the ocean food web; they're the tigers and the lions of the sea; warm-blooded, fast-moving predators. They're a bellwether of marine life. When tuna are in difficulties you can see there is a wider issue."
Still, there's always the skipjack, isn't there? No matter how many are fished, their populations don't seem to be dented. But the rule of fishing scientists is that an unregulated fishery is an unprofitable fishery in the long run, because we keep on fishing until there's nothing left. This is what happened to the abundant cod that disappeared off the Grand Banks of Canada in the early 1990s. They have never returned.
"There's a limited ability of everything to escape," warns Roberts. "What you find is that things that are incredibly robust and resilient end up in trouble. And they can collapse very quickly. Few people predicted the collapse of the cod off the Grand Banks of Canada. I wouldn't count on skipjack being too hard to fish out."
Know your tuna: A diner’s guide
Atlantic bluefin (THUNNUS THYNNUS)
Also called: Northern bluefin; hon maguro (Japan); roter thun (Germany)
Percentage of global catch: less than one per cent
A delicacy since Roman times, when soldiers gorged on its entrails before battle, the Atlantic bluefin can grow to more than four metres in length and swim at 45mph. Delicious as sashimi it is highly prized, selling for over £62,300 per fish at Tokyo fish markets. Demand has hammered stocks by 90 per cent since the 1970s in some waters. Celebrities including Elle Macpherson and Stephen Fry have recently petitioned the London sushi restaurant Nobu to take Bluefin off its menu.
Southern bluefin (THUNNUS MACCOYII)
Also called: bach maguro (Japan); nan fang hay we (China)
Percentage of global catch: less than one per cent
The Southern species has declined by about 92 per cent since industrial fishing began in the 1950s, making it “critically endangered” according to the International Union for Conservation of Nature (IUCN). The fish, which is prized as sushi and is found in the southern hemisphere waters of all the world’s oceans, is now protected by the Convention for the Conservation of Southern Bluefin Tuna in Australia. But Japan has been accused of overfishing its quota.
Pacific bluefin (THUNNUS ORIENTALIS)
Also called: thon rouge (France); tuna sirip biru Pasifik (Indonesia)
Percentage of global catch: less than one per cent
Just as delicious, just as majestic and just as imperilled as its Atlantic sister, the Pacific bluefin spawns in the waters between Okinawa and the Philippines before migrating 6,000 miles to the Eastern Pacific. They can live for up to 25 years but are often caught before they have a chance to breed and are considered to be as endangered as pandas; Charles Clover calls them the “blue whale of our time.”
Albacore (THUNNUS ALALUNGA)
Also called: white tuna; tombo; germon (France); Bonito del norte (Spain)
Percentage of global catch: six per cent Stock records are scant but the 140cm fish is thought to be endangered in the Altantic due to overfishing; it fares better in the Pacific. Generally caught when they are older than other tuna, some Albacore have been shown to have higher levels of mercury, leading some food organisations to advise against eating large quantities. Milder in flavour than other species, the fish is usually canned but can be sold as steaks or sushi. In the US it is the only fish that can be marketed “white meat tuna”.
Bigeye (THUNNUS OBESUS)
Also called: Grossaugenthun (Germany); patudo (France); ahi (Hawaii)
Percentage of global catch: 10 per cent
Classified as “vulnerable” on the IUCN Red List, the Bigeye grows up to 250cm in length. It often comes a cropper thanks to its affinity for flotsam, which means it’s a sitting duck when nets are floated on the water’s surface. It also matures later than other species but impatient fisherman often snare the fish before they can breed, hastening the species’ decline. The second-most desirable tuna among sushivores, the Bigeye may suffer further as diners wean themselves off bluefin.
Skipjack (KATSUWONUS PELAMIS)
Also called: bonito, skippy, tonnetto striato (Italy), barrilete (Spain)
Percentage of global catch: 51 per cent
It’s likely that the content of those cans in your cupboards started life, perhaps some time ago, as skipjack. The poor relative of the tuna family grows to about a metre in length and exists in huge shoals in tropical waters globally. Also used to make fish stock in Japan, the sandwich staple is not considered endangered but irresponsible, industrial fishing with nets often threatens other species. Greenpeace petitions supermarkets to source only skipjack caught by line.
Yellowfin (THUNNUS ALBACARES)
Also called: yellowfinned albacore; gelbflossenthun (Germany); huang chi we (China)
Percentage of global catch: 32 per cent
The second most common tuna after skipjack, the yellowfin is becoming a popular replacement for the severely depleted Southern bluefin. It is widely used in sashimi and lightly-seared steaks, while lower-grade specimens are often canned. Stocks have been decreasing steadily since the 1970s and 1980s, although the IUCN includes the species in its “least concern” category. But conservationists are worried that, like the bigeye, the yellowfin may become more endangered if governments don’t impose stricter quotas as the bluefin escapes the clutches of our chopsticks.