They're enormous, abundant and so sustainable it's practically our duty to eat them. So can Britain's foodies be converted to Norwegian king crabs? Tim Walker reports

They're big in Japan. They're big in the States. They're just, well, big. Now, thanks to Pascal Proyart, pioneering seafood chef at Knightsbridge restaurant One-O-One, Norwegian red king crabs are invading Britain.

After they were introduced to the Barents Sea by Russian scientists in the 1960s, the king crab's numbers grew exponentially. By the 1980s they had been found in Norwegian waters. Now they rule the waves of the Arctic, and the Norwegians have to catch them to prevent overcrowding. They're so prevalent that it's practically our duty to start eating them so forget about those dwindling cod stocks, crabs are the sustainable seafood.

Proyart is giddy as a Breton schoolboy as he watches the day's catch being winched up from the icy depths of the Barents. The cages are brimming with crab, and he plunges a hand into the mass of pink limbs to yank out the pick of the crop, holding the beast affectionately with both hands. It's a whopper, with a body the size of a football and legs almost as long as mine. Back in London, he'll serve the central cannon of this sea monster's leg with sweet chilli and ginger, in a risotto with a Parmesan pancake, or alongside roasted pigeon sourced from Anjou, near his home in north-west France.

The chef was first introduced to king crab by a Norwegian fisherman when he was a chef in Brussels in the early 1990s. He popularised the dish there before moving to One-O-One in 1995, bringing the tasty crustaceans with him. "I was the first chef in London to serve them," he says. "When I said 'king crab' to other restaurateurs, they all looked at me like I was mad. They asked 'Is that the stuff that comes in tins?'" Now about 10 of London's top restaurants serve Norwegian king crab, among them is The Capital, the kitchen of which is run by Proyart's friend and fellow Frenchman Eric Chavot. "The kitchen at One-O-One shifts about 50kg of crab each week now," Proyart boasts, "60 or 70 in high season."

Seafood is Norway's second-largest export after oil and gas, and the Norwegian Seafood Council claims that 27 million meals using Norwegian seafood are consumed worldwide every day. However, king crab fishing only became a commercial endeavour for the Norwegians in 2002, when they negotiated a quota (now about 300,000 male crabs per year) with the Russians, who still see it as their species.

Russian scientists put a sample of the crabs, which are native to the Pacific, into Western Russian waters in 1961, hoping to provide a new catch for the Soviet fishing fleet and the starving Russian coastal towns they serviced. Their experiment was too successful, and environmentalists warn that the rapid spread of such a voracious species has left a trail of destruction in its wake. The crabs have no natural predators and are themselves omnivores, devouring everything from cod larvae to other crabs. Those same environmentalists maintain that the Norwegian crab-fishing quotas must increase the Barents Sea is overflowing with an estimated 20 million crabs and counting.

Kirkenes, a small town on the far north coast of Norway, just 60 kilometres from the Russian border and well above the Arctic Circle, is crucial to both the energy and fishing industries. It is the gateway to the Barents Sea's vast natural gas reserves, and home to the country's largest king crab fishery. The crabs are caught using small coastal vessels which sail only by day, unlike the weeks spent at sea by their Pacific counterparts. Each boat is allowed to carry a maximum of just 30 nets, so they keep close to the shore, and near to the small processing plant at the village of Burgoynes. Thus each crab is handled and chosen individually smaller specimens are thrown back live into the water and suffers from less stress and damage between the sea and your dinner plate.

Norway still accounts for only a small percentage of the world's total king crab haul, but the Alaskan king crab traditionally popular in Japan, and now widely served in America doesn't measure up, says Proyart, who wears the badge of the Norwegian seafood council on his chef's whites. The average Alaskan king crab weighs in at 3kg, compared with the average 4.3kg of its more substantial Scandinavian cousin. The largest specimens can measure 1.5m across, and weigh a whopping 8kg.

Terry Durack, the Independent on Sunday's restaurant critic, recently named Proyart's Norwegian king crab with sauce vierge and cockles as one of his "unforgettable dishes" of 2007. "Pascal is the one who has introduced England to king crab," he says. "I remember seeing a photograph of him holding one of the things and thinking 'My God! That looks like an alien from outer space!' That's how I became interested in it. When I eventually ate at One-O-One, my eyes were opened. It really has an incredible sweetness. I got the aroma of the ocean in it, the scent of sea spray. The quality of the flesh wasn't spongy or in shreds; it was almost like cod. It really held. Often when you have other kinds of crab it can get a bit stringy and tired in flavour."

Despite their booming numbers, king crabs remain an expensive dinner, available only in a few of London's top eateries. "The only real obstacle to Norwegian king crab being served widely is the expense," argues Durack. "It has incredible flavour; you can saut it, you can steam it, you can have it in stews, have it cold it's absolutely ideal for just about everything, but it is very expensive. You would hope that because it is everywhere it will end up cheaper. If it does, then I'm sure everyone will latch on to it immediately and love it."

If it does get cheaper, then crab might become a serious alternative to cod, haddock and other seafood stocks. Conservation groups were aghast at Environment minister Jonathan Shaw's call for an increase in the UK cod-fishing quota last month. Britain's culinary community is certainly conscious of faltering fish stocks, and modifies its appetite accordingly. "The prevailing view," explains Durack, "is that if cod is from Icelandic waters, then it's OK, but we're unsure about any stocks too close to the UK. Everyone has their own arguments because everyone has their own interests. I know we have to try to take care of our fish populations or else we aren't going to have any left in the oceans. So we are aware and interested in ensuring that we can eat some of the stocks, but still have some left for the future."

While North Sea cod stocks have recovered from the historic low of a few years ago, fisheries scientists aren't convinced they can withstand a return to traditional fishing practices. Newfoundland cod had been fished close to extinction by the turn of this century, and while they are currently in rude health, even Barents Sea cod stocks suffered a collapse in the late 1980s. The Norwegian Seafood Council claims we can eat Barents cod with impunity, but it's where 98 per cent of their cod comes from, so they would say that. The Barents Sea ecosystem nonetheless faces numerous threats from over-fishing, from the increasing transport of oil and gas through its waters, from the storage of radioactive waste, and from the king crab itself.

Fish suppers: guilt-free seafood

* Alaska salmon

The Alaska salmon fishery is the only salmon fishery in the world with Marine Stewardship Council (MSC) certification. What were once unhealthy fish stocks have revived under regulations imposed by the Alaskan state in the 1970s. Harvests rose from about 25 million in 1959 to 214 million in 1999. Alaska salmon is available at Sainsbury's in 'Taste the Difference' sockeye smoked salmon (5.59 for 135g).

* New Zealand hoki

New Zealand's biggest wild-fish export, the rat-tailed cousin of cod is one of the few sustainable white-fish resources. But concerns have been raised about stock levels and the environmental impact of the bottom-trawling methods used by the fishery.

* Pacific cod

The Bering Sea and Aleutian Islands Pacific cod fisheries are the only cod fisheries in the world with MSC certification. Pacific cod has a high growth rate and high natural mortality and can support heavy exploitation.

* Thames herring

One of the first products to carry the MSC logo was our very own Thames herring. Available through most fishmongers and selected branches of Tesco and Sainsbury's, the market for Thames herring is best in the spring.

* Western Australian rock lobster

Producing an average of 11,000 tons of lobster each year, this is the largest and most valuable single-species fishery in Australia with a large market in Asia, America and Europe. Western Australian rock lobster is available at almost all branches of Waitrose for 11.99 each.

* British and Alaskan pollack

A cheap and abundant alternative to cod, the majority of pollack sold in Britain is Alaskan or Pacific. But the species is also found off the West Country coast, so you can dine on sustainable fish and support the Cornish fishing industry at the same time.

Richard Molloy