Marine biologists say not only bluefin tuna but also other fish stocks are plummeting across the world, upsetting delicate natural food chains. Some fear irreversible damage has already been done.

Even worse, international law experts add, little is being done to stop it. Despite all the evidence, high-tech fleets probe the last deepwater refuges, hardly troubled by authorities.

Legal quotas are too high, specialists say, and in any case are often pointless because too many crews lie about their catch.

"This is no sudden crash, but rather an extremely slow-speed fatal collision," Carl Safina, founder of the conservationist Blue Ocean Institute on Long Island in New York, told The Associated Press.

For decades, he said, the world has moved blindly toward a precipice. "We have been confronted with signs and warnings and a clear view of the danger. And now we have fallen off. We may deserve it, but our children do not."

Action is essential

Safina reflected views heard in a broad range of interviews in North America and Europe, from environmental activists to government-financed specialists charged with helping to set fishing limits.

Some are more optimistic, arguing that careful management can restore stocks to sustainable levels, but none dispute that urgent action is essential.

Scientists blame worldwide overfishing by private fleets, often with their governments' complicity. Even where laws and accords are in place, they say, there is seldom more than token enforcement.

With a single bluefin worth as much as $150,000 on the Tokyo market, Italian and Russian organized crime is now involved, U.N. experts say.

Click here for larger image Associated Press

The report, directed by Daniel Pauly, said declassified Cold War technology, aircraft, and U.S. monitoring of water temperatures and ocean bottoms help fisherman find hideouts once beyond their reach.

A later study by Ran Myers and Boris Worm of Nova Scotia's Dalhousie University reported drops of 90 percent among critical stocks. That brought protests from fishing industry officials, who cited other surveys showing smaller declines.

"This is only quibbling over numbers," Safina said. "If it is 60 percent now and not 90 percent, then just wait five years."

Beyond uncontrolled fishing, specialists see damage from pollution, silt runoffs from over-engineered river systems, and the still uncertain impact of global warning.

Bluefin the main prize

Tuna is a particular problem.

Such common varieties as skipjack, found canned in supermarkets, fetch lower prices and are not in immediate danger. But prized bluefins are hunted down for sophisticated worldwide networks of Japanese buyers.

About 20 percent of the world's dwindling supply is caught in the Mediterranean, where tuna stocks are most threatened. And bluefin are also endangered in the Atlantic and Pacific.

In the early 1950s, the global tuna catch was less than 500,000 tons. By 2001, it had surpassed 3.7 million tons.

Serge Garcia, a Frenchman who supervises fish-monitoring programs at the U.N. Food and Agriculture Organization in Rome, says he's deeply disturbed by nearly every trend he sees.

Garcia said the main problem is that since ocean fish cannot be accurately counted, no one can be certain about numbers. As a result, fishermen and conservationists push data to opposite extremes.

But, he said, scientists have a clear idea of the downward trend. "I don't think it is wise to wait until this is proven right beyond any doubt," he said. "By then, it will be too late."

He calculated that fleets should be reduced by 30 percent to 40 percent to preserve stocks.

Ancient methods

The ancient methods of Favignana focused on single schools, in which the biggest fish habitually swim first. This assured a lucrative catch without damage to sustainability.

Now most bluefin are caught on long lines. Other tuna are scooped up by purse-seine nets which catch whatever enters their broad openings. Huge numbers of untargeted fish are dumped back, dead in the water.

Using almost weightless nylon-Kevlar lines up to 2,500 feet long and equipped with lights and tiny cameras, Garcia said, fisherman can find giant old tuna hiding in underwater caves.

The WWF and other groups campaign for fishing moratoriums in sensitive areas as well as rigorous patrols to enforce quotas.

Some experts put hope in tuna ranches, which since have grown fast since 1997. These are not breeding centers, as are common for salmon, but rather holding pens for wild tuna that are caught but not landed.

At 30 Mediterranean sites, captured tuna are held in net corrals for five to 20 months until they fatten.

Proponents say this allows prices to stabilize and adds more meat to the market. But in practice, the WWF says, tuna penning wreaks its own sorts of havoc by disrupting natural cycles and seasonality, and by opening new markets for tuna.