Dolphin-friendly tuna? Don't believe it
Thanks to a growing fashion for sashimi, stocks of bluefin tuna are on the brink of collapse. So which fish should be on the menu? Peter Marren reports
Every chunk of tuna comes from a wild fish. Because tuna are wide-ranging, fast-moving ocean fish, fisheries have developed awesome techniques for catching them. Fleets use vast purse-seine nets to scoop them out of the sea, while Japanese vessels, in particular, trail lines of baited hooks many miles long.
Such methods are undiscriminating. The bycatch - that is, the non-target species - routinely includes sharks, turtles and albatrosses. The ratio is about four sharks caught for every tuna. According to the Shark Trust, longlines operating off New Zealand have snapped up 450,000 blue sharks in 10 years.
Surely supply and demand can save the tuna? It appears that the tuna is rapidly becoming a fashion victim.
Two things are combining to bring down the bluefin. One is their slow breeding rate -they take at least 10 years to become sexually mature, and so are vulnerable to overfishing.
The other problem is that bluefin are expensive. A full-sized fish can fetch tens of thousands of dollars. And a market that was once centred in Japan is widening by the year. Many countries, including Britain, have acquired a taste for sashimi - thin slivers of raw tuna dunked in soya sauce. Last year we imported 1,600 tons of the stuff, worth £8.6m. But that is small beer compared with the potential market in China, where a fast-growing middle class eyes bluefin sushi as the ultimate gastronomic status symbol.
This isn't sustainable. Although bluefin can be farmed, no one has yet worked out a way of rearing them from eggs. All farmed tuna are simply wild-caught from the sea and fattened up. But stocks are becoming dangerously depleted. Catches around the Balearic Islands are down to just 15 per cent of what they were a decade ago, and six Spanish tuna farms have gone out of business.
This species is currently classed as "critically endangered". Without urgent intervention, the southern bluefin is probably doomed to commercial, if not actual, extinction. But so long as Japan continues to allow only Japanese inspectors on board its fishing vessels, and refuses to install satellite monitoring systems, there is no way of checking its catches. All scientists know is what that country imports. It looks like stalemate unless Japan can be persuaded to see reason.