It was one of the most expensive fish ever sold. A few weeks ago, a giant bluefin tuna achieved a price of 16.3m yen – about £111,000 – at auction in Tokyo. The rich, buttery taste of the tuna's flesh made the 513lb fish irresistible for one group of restaurateurs. The bluefin's fillets ended up on hundreds of sushi platters across Tokyo within hours of the sale.
But deals such as these may soon become a thing of the past. Scientists, politicians and wildlife groups are pressing for trade in the bluefin tuna to be restricted at the forthcoming meeting of Cites, the Convention on International Trade in Endangered Species, in Doha, Qatar.
In particular, they want the Atlantic bluefin, the species that is suffering most from overfishing, to be given appendix-1 status by Cites when it convenes next month. The proposal, put forward by Monaco, would end trade in the tuna between European fishing fleets and Japan, the world's main purchaser of the fish. Not surprisingly, Japan is expected to oppose the ban, the bluefin being a prime ingredient for sushi.
"Stocks of bluefin tuna in the western Atlantic have dropped by 82% since 1978, while those in the eastern Atlantic have dropped by 80%," said Heather Sohl, of the WWF. "We are looking at a species that is going to be fished into extinction unless we take urgent measures to save it."
The bluefin tuna can grow up to 14ft in length, weigh more than 1,000lb (450kg) and live for more than 30 years. It can swim at up to 40mph (65km/h), can dive to depths of half a mile and is one of the oceans' great travellers, swimming from the tropics to the Arctic. However, it has become an increasingly popular target for trawler fleets from France, Spain and Italy, who have found a lucrative market in Japan.
"Moving the bluefin to appendix 1 of the convention would not ban the catching of them, but it would prevent European fishing fleets selling them to Japan," said Sohl. "That would be hugely effective."
Experts also warn that the banning of trade would not end the sale of tuna in restaurants and stores. Of the other species of tuna, including yellowfin, skipjack, bigeye and albacore, the skipjack is the only one not suffering from serious population decline linked to overfishing. The problem, add scientists, is that a ban on trade in the bluefin could lead to increased fishing of the other species.
In addition, campaigners say the overfishing of tuna poses other risks. The collapse of bluefin numbers in the Mediterranean threatens to trigger disruptions throughout the food chain. Squid numbers could rise in the absence of their tuna predators, which could adversely affect the sardine population.
It is estimated that about one million bluefins were caught last year, while the total population is thought to be about 3.75m. "That greatly exceeds the power of the species to replace its numbers," said Sohl.