The fishing season opens today in the Mediterranean spawning grounds of the “king of sushi” — the bluefin tuna — with a grim warning that current catch rates mean it will die out in as little as three years.

Bluefin has become such a soughtafter delicacy in the Far East that ever higher prices are being paid for one of the ocean’s swiftest predators — and the rich red meat that makes it so desirable. But the size of the individual fish caught each year has dropped and conservationists fear that even recent restrictions imposed by the European Union will not save enough adults to keep the bluefin stocks viable.

Its demise is blamed on the introduction of fishing vessels in the 1990s that can round up 3,000 bluefin in one go. Most of the fish are frozen for air-freighting to Japan. The price depends on the fattiness of the meat with a record set last year in Tokyo’s Tsukiji Market of $55,700 (£37,400) for a 276kg (608lb) fish.

“For years people have been asking when the collapse of this fishery will happen, and now we have the answer,” said Sergi Tudela, Head of Fisheries at WWF Mediterranean, who is calling for a ban on bluefin fishing in the Mediterranean while stocks recover.

“Mediterranean (Atlantic) bluefin tuna is collapsing as we speak and yet the fishery will kick off again tomorrow for business as usual. It is absurd and inexcusable to open a fishing season when stocks of the target species are collapsing," he added.

WWF said that analysis of official data showed that the average size of mature tunas had more than halved since the 1990s.

New EU rules will cut bluefin quotas by 2011 and shorten the period in which the species can be fished from six months to two, with a freeze on fishing capacity this season.

Illegal practices such as using spotter planes are still said to be used by unscrupulous fishermen determined to profit from the lucrative fish.

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