Scientists warn on Thursday that the Atlantic bluefin tuna faces extinction unless urgent action is taken.
They used electronic tags to track the migration of the powerful fish from the Gulf of Mexico to the Mediterranean, and report on Thursday in the journal Nature that nutritious meals of sushi, salade niçoise and tuna melt sandwiches worldwide are more at risk than anyone had imagined.
The bluefin tuna can live for 30 years, grow to three metres in length and weigh as much as 700kg. A prime specimen can fetch as much as $100 000 in the Tokyo fish markets.
”In my lifetime we’ve bought this majestic species to the doorstep of ecological extinction in the Western Atlantic Ocean,” said Barbara Block of Stanford University in California. ”Electronic tagging provides the best scientific information we’ve ever had to manage these tuna and we must, as an international community, start to act responsibly to ensure the future of this species.”
Marine scientists have repeatedly warned that the harvest of the seas has become unsustainable. The cod fishery off Newfoundland is exhausted, North Sea and Iceland stocks are under threat, so fishermen have pushed further offshore in search of deep ocean fish.
Tuna — always a delicacy in the Mediterranean and Japan — has been under increasing pressure for decades. The International Commission on the Conservation of Atlantic Tuna has tried to manage the fish since 1969.
There are two populations: A western one that has declined by 80% in the past 30 years, and a larger, eastern population. Although catches are in theory controlled by quota — 3 000 tonnes a year in the western fishery, 32 000 in the eastern range — no one knew enough about the wild tuna to be sure the limits worked.
So Block and her colleagues placed electronic tags on hundreds of the fish and tracked them to depths of more than 900m and on journeys of thousands of kilometres, measuring the migration pattern, diving behaviour, body and water temperatures.
The research published on Thursday confirms that separate quotas may not be the answer, because tuna do not recognise any boundaries and can voyage in subpolar seas. So the two populations mix,
”There are two ways to save the Atlantic bluefin tuna stock — protect them in their breeding grounds and in their feeding grounds,” Block said. ”This will require immediate action in both the central Atlantic, to reduce the mortality of the giant bluefin while foraging, and in the Gulf of Mexico and Mediterranean, where bluefin breed as discrete populations.” – Guardian Unlimited Â