Experts say too many of these majestic fish prized since Greek and Roman times - each one of which can weigh up to 900 kilos - are ending up on the platters of restaurants around the globe.

"Japanese consumption was already a threat to bluefin tuna in the Mediterranean. The European craze for sushi bars has added to that," said Roberto Mielgo Bregazzi, a Spanish expert and author of several reports for Greenpeace and the World Wildlife Fund.

"If the Chinese market continues to grow, that will be the end of the stock," he said.

Eating Japanese-style raw fish in rice packages spread to Europe and the United States in the 1990s and quickly grabbed palates there.

China seems to be next, according to Mr Bregazzi, who said there had been a significant increase in tuna consumption there in the past six years.

Even though there are few official figures on Chinese consumption, the trend has also been observed by the International Commission for the Conservation of Atlantic Tunas (ICCAT), a body responsible for managing bluefin tuna fishing.

Japan, however, remains the main consumer of bluefin tuna.

"Around 80 to 85 per cent of bluefin tuna caught in the Mediterranean is exported to Japan," said Jean-Marc Fromentin, a leading worldwide expert on the subject at the French Research Institute for Exploitation of the Sea (IFREMER).

Sushi consumption took off after World War II, largely using southern bluefish tuna then found in huge numbers off the coast of Australia.

"This stock has now collapsed thanks to over-fishing, and the Japanese turned their attention to the Atlantic bluefin tuna," said Mr Fromentin, adding that despite its name, Atlantic bluefin comes mainly from the Mediterranean.

Prices began to climb. Fishing fleets were modernised in Europe and new fishing fleets created in Turkey and northern Africa. The result - a huge over-capacity in fishing.

Today more than 50,000 tonnes of bluefin tuna are caught every year in the Mediterranean. To prevent stocks from collapsing, that figure should be limited to 15,000 tonnes in the short term, according to ICCAT.

"The bluefin tuna industry is in the process of fishing itself to death," Greenpeace oceans campaigner Karli Thomas said.

The risk now is that the depletion of tuna will wipe out the fishing sector and cost thousands of jobs in the Mediterranean region.

Former Beatle Paul McCartney is urging the world to go vegetarian in a bid to fight global warming and is surprised more green groups do not promote it.

In an interview with the animal rights group People for the Ethical Treatment of Animals (PETA), McCartney said the global meat industry was a major contributor to global warming.

"The biggest change anyone could make in their own lifestyle would be to become vegetarian," McCartney, a long time vegetarian and advocate of vegetarianism, said.

"I would urge everyone to think about taking this simple step to help our precious environment and save it for the children of the future."

McCartney says the amount of land and water used to maintain the meat industry makes it a major contributor to climate change and complains that most environmental groups do not list vegetarianism as one of their top priorities.

"It's very surprising that most major environmental organisations are leaving the option of going vegetarian off their lists of top ways to curtail global warming," he said.

A 2006 United Nations report found that cattle-rearing generated more greenhouse gases than transportation.

- Reuters