Save the world by eating sushi

With tuna and salmon stocks dwindling, an oily fish from southeast Asia offers a sustainable substitute. But does cobia pass the taste test? Rob Sharp finds out

Britain's beleaguered fish stocks, bombarded by years of overfishing, are dying. Our fishermen have hoisted haddock and hooked hake for decades. Some studies suggest modern fishermen have to try 17 times harder to secure the same catch as their Victorian counterparts. The situation is reaching crisis point. One belly-full of fishy food can destroy generations of slimy swimmers. As sustainable fishing becomes increasingly important, where can our nation's chefs turn for environmentally-friendly yet tasty fish cuisine?

Salvation could come in the form of a dark-backed, tuna-like oily fish from south-east Asia. It doesn't like the cold, grows three times faster than Atlantic salmon and can be barbecued, grilled, fried or eaten raw. Swim to your marks, cobia, for you could soon become the biggest fish in Britain's long-suffering culinary pond.

The white-fleshed cobia, a popular North American game fish that is generally not caught commercially, is being launched in Britain by Marine Farms, a Norway-based fish farming company. The business is assessing interest in the fish, which it hopes to market as an alternative to salmon and tuna for sushi. Because of its sturdy, dense texture, which allows it to be easily chopped to a number of desired sizes, the company's representatives say it could also replace cod as the fish of choice on Britain's dinner tables.

"We noticed the fish's potential back in 2002 and purchased a hatchery in Florida but struggled to produce it," says Marine Farms' chief executive Bjørn Myrseth. "Since then it's been a labour of love, 10 years in the making, but we eventually found somewhere in Vietnam where the climate was just right to produce the fish. Then, bingo. We're hoping that when people taste the quality of the product – its texture, its flavour, and the speed at which it can be produced – they will take to it as much as the more traditional fish served over here".

Myrseth, who studied to train as a fisheries biologist in his native Norway before going on to spend some 40 years in the fish farming business, came across cobia at a trade conference in Taiwan. Some farmers had bred it in captivity and were producing a relatively small 2,000 tonnes a year. "There isn't much of a tradition for cooking cobia," continues the fish farmer. "While it's a tropical fish it's not caught in large quantities. I have mainly eaten it as a sashimi, dipping it in soy sauce, and it was delightful. I visited a couple of the farms, learned the fish's biology and found out Taiwan's cold winters and typhoons are not perfect conditions in which to farm it. There had to be something else."

Myrseth took the animal to Florida, Belize and Vietnam; it floundered in the relatively warm waters of the US west coast but flourished in the other locations. He now uses Belize to serve the North America while Vietnam supplies south-east Asia and Europe. Marine Farms expects to produce 1,500 tonnes this year for export. The Vietnam site could produce 6,000 tonnes annually.

So how does the fish measure up? Is it as tasty as its fans claim? We managed to lay our hands on one of the only two pieces of cobia in Britain and took it to Lee Bennett, head chef of London riverside French restaurant Le Pont de la Tour, a man who trained for several years under the censorious gaze of Gordon Ramsay. Transporting the fish across London in an ice-full cool bag was just half the battle – would it impress one of the most talented young chefs in Britain?

"The first thing I'm looking for is taste," says Bennett, barking orders across his busy kitchen and deftly cutting the pre-filleted fish into oblongs before slicing and dicing it. "Initial impressions are that it looks like a smallish white tuna. If it's a new fish, it really has to be exemplary. In a recession people stick to what they know." The chef is complimentary on the fish's ability to hold up when he cuts it; its density lends it robustness, automatically lending it to use in sushi and sashimi. To taste, it is very mild, making it versatile, though likely to be overpowered by soy sauce, pickled ginger and wasabi.

Bennett chops up the fish and mixes it with diced shallots, Dijon mustard, lime juice and zest to make a tartare. He would normally use mackerel; in this case, around 80 per cent of the flavour comes through the lime and mustard. The chef tries pan-frying a large chunk, with a small amount of oil, while basting it with butter. Because of its density, it is cooked for two minutes to prevent it drying out; though this inevitably means a large amount of the fish is undercooked.

In smaller slices it works better; it is tastier the cod the chef fries alongside it, though Bennett says the cobia's relatively tough texture is a bit of a turn off. Again, it is easy to tell it would be very easy to overcook. When tried with strong-tasting vegetables like asparagus, again, the fish's taste is overpowered. Conclusion: it's probably best for raw. If it's pan fried, it needs to be served with mild vegetables and possibly a mild white wine.

One final question presents itself. If this is being marketed as a sustainable, environmentally-friendly fish – Myrseth claims all Marine Farm cobia is farmed in low-density ocean cages with site rotation to prevent disease and damage to the environment – doesn't the trip from Vietnam create a hefty carbon footprint?

"It is not possible to farm the fish in Europe," is Myrseth's answer. "It has to be farmed in the tropics. It is an alternative to wild fish in Europe and aims to take pressure off their fishing. When the fish is flown it has a high carbon footprint; when it is container shipped it is much lower." Does that sell it for you? It remains to be seen whether this cool customer manages to reel in the eco-conscious fish-o-philes.

More sustainable fish to try

Pollack

The primary alternative to haddock or cod, its flesh has a firm texture and delicate taste. Caught off the Cornish coast by shallow trawling, this is an eco-friendly British option, though lacking in distinctive flavour.

Black Bream

Found off Cornwall and southern Wales. Sweet and reassuringly firm, it can be eaten raw, in a salad or in sushi, or cooked in a simple dish.

Western Australian Rock Lobster

The most valuable species fished in Australia, available in Waitrose. This crustacean has a tough texture and a rich, salty flavour. A deep-fried delicacy in the Antipodes.

Whiting

As stocks have dropped, whiting is on the rise. Traditionally passed over, its growing abundance in the Channel has made it a local choice. Its flesh is tender and has a slight taste, which makes it perfect for a pâté or mousse.

Cuttlefish

Deceptively named, these creatures are part of the mollusc family. Perfect for a BBQ or the classic Italian dish Risotto al Nero di Seppia, where the ink darkens and flavours the sauce. Common in the English Channel. David Whelan