Cod taken off the shelves at Asda to preserve stocks

Asda, Britain's second biggest supermarket, is removing North Sea cod from its shelves in response to the dramatic collapse of natural fish stocks.

In a sign of how overfishing has devastated the once-plentiful cod off Britain's coast, the supermarket said that it would suspend sale of North Sea cod by July. It said the move had been influenced by attacks from environmentalists for its sale of endangered fish such as cod, which is heading towards commercial extinction in the waters off Britain.

Greenpeace demonstrators scaled the roof of Asda's Leeds headquarters in January and unfurled a banner that read: "Will stocks last?" while the Marine Conservation Society ranked the store bottom for sustainable fish sales. In a self-declared conversion to environmentalism that includes selling sustainable hardwood and raising prices to dairy farmers, Asda said that as well as suspending North Sea cod, it would cease the sale of swordfish, which is also endangered.

The chain said that it intended to follow its parent company Walmart within five years by selling only fish certified by the Marine Stewardship Council, the London body which checks global fisheries for sustainability and legality. The move could make Asda among the most ethical supermarkets for fish - a distinction currently held by Marks & Spencer and Waitrose.

But Asda went one step further by suggesting that the whole of the North Sea should be turned into a marine conservation zone with commercial fishing limited to local boats to protect it from overfishing.

Green groups welcomed the supermarket's commitment, which they said highlighted how the ravaging of the seas was rising up the agenda of UK shopkeepers and consumers, who spend £1.8bn a year on fish. Overfishing has decimated stocks of cod, skate, monkfish, hake any many other species, resulting in the estimated loss of 90 per cent of the world's big fish such as tuna, swordfish and marlin.

Cod's global decline has been particularly stark. Stocks off Newfoundland, Canada, collapsed in the early 1990s and have not recovered, in a grim portent of what night happen in the North Sea. Historically, cod have teemed off British shores - fishermen from Scotland and the east of England were helping to land 300,000 tons a year in the 1970s and 1980s. But, for the past four years, the International Council for the Exploration of the Seas - the scientific body which advises the EU on its common fisheries policy - has urged all cod fishing in the North Sea to stop.

Politicians in the European Commission have repeatedly ignored the advice and, this year, set a catch of about 23,000 tons - almost half of the remaining stock.

Blake Lee-Harwood, Greenpeace's campaign director, said Asda's move highlighted how store chains were rapidly "delisting" endangered species.

"It's one of those issues whose time has come and I think supermarkets have been looking at themselves and have thought: 'We can't really justify selling the last cod in the North Sea.'"

He believed consumers still had little idea just how overfishing has harmed stocks - 75 per cent are over-exploited. He said: "People think [the sea] is so vast we cannot possibly catch all the fish. If you have any experience of the fishing industry, you realise it is only too possible."

Bryce Beukers-Stewart, fisheries policy officer at the Marine Conservation Society, said: "The warnings about overfishing have been going on for years and suddenly supermarkets are reacting.There's a lot of competition between supermarkets: as soon as you perceive that selling sustainable fish is beneficial, everyone jumps aboard."

Fish to avoid

* Atlantic Cod: overfished. Eat well-managed Icelandic cod.

* Monkfish: over-exploited, long-lived

* Marlin: predator plays an important role in marine eco-system. Over-fished.

* Seabass: avoid trawl fisheries that kill dolphins. Choose line-caught seabass

* Skates and rays: endangered, slow to mature

Fish to eat

* Herring: plentiful in North Sea. Contains Omega 3

* Salmon: organic farmed better for the environment

* Hoki: New Zealand white fish. Treat like cod

* Red Gurnard: fast growing and liked by chefs

* Alaskan Pollock: sustainably fished

Source: Marine Conservation Society