Michael McCarthy: Deadly, delicious and, very possibly, doomed

We all know what mackerel looks like. Even on the fishmonger's slab it seems streamlined and sleek for slicing through the water, a silvery predator designed for pursuit. Ted Hughes admired it so much he wrote a hymn to it ("Mackerel Song").

Now imagine a mackerel cousin, a giant one, 12 feet long and weighing half a ton, a creature that even with such size can shoot through the sea at more than 40mph, and there you have Thunnus thynnus, the bluefin tuna.

In some ways it is the ultimate fish. Bluish above, silver below, it is the Ferrari, the Maserati, the Lamborghini of the sea, a big-engined powerful hunter with sports car design and, you might say, sports car extras. It is warm blooded, but able to regulate its own internal temperature which means it can roam at will the cold oceans and the warm, from the north Atlantic to the southern Mediterranean. It is also, unfortunately for the future of the species, one of the ultimate fish to eat.

It is undoubtedly delicious, reflected in the fact that its culinary qualities have been celebrated for thousands of years. Greek writers from Aristotle down wrote about it; the Romans loved it; and every Mediterranean country has hunted it since organised sea fishing began. For these countries, there was always enough to go round.

Now, however, it is faced with the appetite of Japan, a country of 127 million fish lovers who prize bluefin tuna above almost everything else, and are prepared to pay inordinate sums for one of the fish. Add modern fishing techniques to that insatiable demand, and it is easy to see why Thunnus thynnus is facing the bleakest of futures.