Leading article: An encouraging tale from the North Sea

For many of us, North Sea cod has been the most vivid illustration of the collapse of global fish stocks.

The decline of a species which was once so cheap and plentiful that it formed the basis of our national dish is an episode worth revisiting. Marine scientists have no exact figure for the historic, natural level of cod in our waters, but we can be sure it is now a fraction of that which existed prior to industralisation, when boats mechanised and sailed further out to sea.

And more recently the collapse of North Sea cod, driven by the recklessness of European Union fisheries policy and an overpowered fishing fleet, has been stark, unrelenting and depressing. In 1970, the spawning biomass of North Sea cod was 250,000 tons. This sank to an historic low of 35,700 in 2006 before rising to an estimated 54,250 this year. This revival has not come about by chance.

Conservation methods undertaken by the Scottish fishing fleet, such as using wider meshes and throwing fewer small fish back into the sea, have minimised the absurd wastefulness of the EU's common fishing policy. The skippers of the whitefish fleet, which has shrunk to a third of its former size through decommissioning, are all keenly aware now that they must conserve and replenish cod.

Against this encouraging news, however, must be set the ongoing worldwide decline in global fish stocks. We have already eaten an estimated 90 per cent of the world's predatory fish, and this weekend will see the recommencement of the bluefin tuna fishery in the Mediterranean, which looks destined finally to drive that fish to commercial extinction.

The dangers of fishing out a sustainable and cheap source of protein and its consequences for the human diet in a rapidly populating world cannot be exaggerated. We need to act decisively to prevent this. And the fishermen who ply their trade in the chilly waters of the North Sea have shown the way.