All fishing should be banned in a third of the world's oceans to reverse a catastrophic decline in fish stocks such as cod and tuna, British scientists have warned.
In a new study, they recommend that large areas of ocean, including the North Sea, around the Falklands, and the Gulf of California, should be made into legally protected marine reserves, policed by naval patrols and satellites.
The dramatic proposal - expected to be endorsed by an international conference on wildlife reserves next month - follows mounting alarm about the worldwide collapse of fish, dolphin, whale and turtle populations, and the destruction of ancient coral reefs.
Professor Callum Roberts, a marine biologist at York University and co-author of the study, said the world's oceans were now in crisis. "We've now reached the terrible and unstable state where we're fishing species so heavily that there are virtually no reproductive fish around," he said.
Last Thursday, the scale of that crisis was underlined when scientists with the Scottish Fisheries Research Service warned that North Sea cod stocks, now down to about 40,000 tonnes, were "critical" and called for fishing to be heavily restricted.
That day, Australian and South African fishery protection vessels apprehended a Uruguayan trawler after a three-week chase, for illegally catching the endangered Patagonian toothfish. Known as "white gold", the fish was thought to be worth $2m (£1.4m) on the black market.
Prof Roberts, who will address the World Parks Congress in Durban, South Africa, next month, said both cases underlined the need for a global network of ocean reserves, or marine protected areas, where fish stocks and coral could fully recover.
The use of modern trawlers with nets capable of reaching great depths, fishing lines that stretch for 130km and holds that can freeze thousands of tonnes of fish meant that very few oceans were left unfished, he said.
The magazine Nature reported last month that 90 per cent of large fish stocks had been removed worldwide. In areas such as the North Sea, trawlers were legally allowed to catch young fish before they could reproduce.
Prof Roberts described this practice as "crazy". "Imagine if on land we were to plough up everywhere. But we don't - we protect large areas for its landscape, for its wildlife and its inspirational value. Yet, with the sea, we're ploughing it all up ... We don't have anything like the number of protected areas necessary."
In his new report, published by the journal Trends in Ecology and Evolution, he and his colleague Dr Fiona Gell analysed 300 studies of 60 small marine reserves, which showed clear evidence that reserves will rebuild decimated populations.
Closing 10-15 per cent of a fishing ground for at least five years, they found, would preserve local marine life. But closing off 30-40 per cent of that area would allow fish stocks to recover to commercial levels, spilling over into the surrounding area. Far from killing off local marine industries, that would give local fleets a new lease of life.
Their case studies included a 2sq km area near the Isle of Man, where a ban on trawling and dredging has led to a sevenfold increase in scallop numbers within 11 years. In one South African reserve, Tsitsikamma National Park, seabream numbers are up between seven and 21 times compared with fishing areas nearby. In the Long Island-Kokomohua reserve in New Zealand, fish were 39 per cent bigger on average. In the Philippines, coral reef species in Apo Island reserve increased eightfold.
Dr Gell said: "Stocks typically expand between two and five times in just five years of protection. Benefits continue to grow for decades as populations of long-lived species recover."
The World Parks Congress, held every 10 years, is expected to pass a declaration calling for a substantial global network of marine reserves to be in place by 2012.
The Roberts-Gell report is the first time that scientists have made specific recommendations on the scale of marine reserves.
The UK Government has signed up to two international pledges for a network of reserves - at the World Summit on Sustainable Development in South Africa last year, and at a North Atlantic marine pollution conference in Bremen in June. And, under the Ospar pollution treaty, European governments have pledged to draw up a list of marine reserves by 2012. However, many conservationists claim that this could be too late and believe more urgent action is required.
Research by Nadia Iqbal
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Patagonian toothfish (Falkland Islands and Patagonian Shelf): Dissostichus eleginoides lives in the Falklands area - one of the world's richest marine ecosystems, teeming with penguins, unique seabirds, squid, whales, seals and fish.
Kemp's turtle (Gulf of California, Mexico): Lepidochelys kempi is close to extinction. Devastated by shrimp fishing, only a few hundred nest each year in the Gulf of California - the home to manta rays, whales and sharks.
Cod (North Sea): The common cod, Gadus morhua, is under severe threat in the North Sea from overfishing. The central North Sea's coral reefs are a crucial home and spawning ground for marine life. Banning fishing would allow cod, halibut and hake to recover.
Bluefin tuna (Florida coast): Due to overfishing off the US Atlantic coast Thunnus thynnus is now critically endangered. It could recover if Florida's east coast was a reserve; the area is full of marine life, including large tuna, swordfish and Olive Ridley turtles.
Whale shark (Philippines): Uncontrolled hunting of rhincodon typus for meat and highly prized fins led to a global ban on its sale. It lives near the Philippines, home to the world's richest coral reefs and a "hot spot" for whales and dolphins.Reuse content