Tuna's spawning grounds under threat

Procida, Italy - Just off this picturesque Italian island, a fortune is fattening in two giant, underwater cages.

Almost every day, workers dump five tons of thawed herring or mackerel into the water to feed more than 250 tons of giant bluefin tuna, which were caught hundreds of miles away and will eventually be sold to Japan, where it is highly prized for sushi and sashimi.

This tuna farm is part of a vast industry that environmentalists say is rapidly driving the bluefin tuna, one of the largest and most prized fish species in the Mediterranean, toward collapse.

Fisheries in Norway and Germany have already disappeared, but the collapse of the Mediterranean stock, scientists say, would devastate the species. The salty, warm waters of the Mediterranean are one of only two places in the world where the Atlantic bluefin spawn.

Mediterranean-wide quotas exist for bluefin, which is the only fish in the region for which such regulations have been implemented. But these quotas are twice what scientists recommend and, environmental groups say, they are poorly enforced.

An independent report commissioned by the World Wildlife Fund found that while Spain declared it had caught only 4,700 tons of bluefin in 2006, it reported exporting more than 9,000 tons. And this year, France and Italy admitted to catching far above their allocated quotas.