Ecolofish's catch was part of an annual legal take of 32,000 metric tons in the Mediterranean and eastern Atlantic. The true quantity, however, is closer to between 50,000 metric tons and 60,000 metric tons. The group charged with managing bluefin tuna stocks, the International Commission for the Conservation of Atlantic Tuna (ICCAT), has acknowledged that the fleet has been violating quotas egregiously. Scientists estimate that if fishing continues at current levels, stocks are bound to collapse. But despite strong warnings from its own biologists, ICCAT—with 43 member states—refused to reduce quotas significantly last November, over the objections of delegations from the U.S., Canada, and a handful of other nations. Because bluefin sometimes migrate across the Atlantic, American scientists, and bluefin fishermen who abide by small quotas off their coasts, have long been calling for a large reduction in the Mediterranean catch.

"The Mediterranean is at the point that if bluefin stocks are not actually collapsing, they are approaching collapse," said William T. Hogarth, ICCAT's recently appointed chairman, who also serves as director of the U.S. National Marine Fisheries Service. "I was really disappointed—when it got to bluefin, science just seemed to go out the window. The bottom line was that, as chairman, I felt I was sort of presiding over the demise of one of the most magnificent fish that swims the ocean."

The story of giant bluefin tuna began with unfathomable abundance, as they surged through the Straits of Gibraltar each spring, fanning out across the Mediterranean to spawn. Over millennia, fishermen devised a method of extending nets from shore to intercept the fish and funnel them into chambers, where they were slaughtered. By the mid-1800s, a hundred tuna traps—known as tonnara in Italy and almadraba in Spain—harvested up to 15,000 metric tons of bluefin annually. The fishery was sustainable, supporting thousands of workers and their families.

Today, all but a dozen or so of the trap fisheries have closed, primarily for lack of fish but also because of coastal development and pollution. One of the few that remains is the renowned tonnara, founded by Arabs in the ninth century, on the island of Favignana off Sicily. In 1864, Favignana's fishermen took a record 14,020 bluefin, averaging 425 pounds (190 kilograms). Last year, so few fish were caught—about 100, averaging 65 pounds (30 kilograms)—that Favignana held only one mattanza, which occurs when the tuna are channeled into a netted chamber and lifted to the surface by fishermen who kill them with gaffs. One sign of the Favignana tonnara's diminishment is that it is run by a Rome marketing executive, Chiara Zarlocco, whose plan for the future is to dress the fishermen in historic costumes as they reenact the mattanza.

The big trouble for Atlantic bluefin began in the mid-1990s. By then, stocks of southern bluefin tuna—which, along with Pacific bluefin and Atlantic bluefin, compose the world's three bluefin species, all treasured for sushi—had been fished to between 6 and 12 percent of the original numbers in the South Pacific and Indian Oceans. As the Japanese searched for new sources, they turned to the Mediterranean, where bluefin reserves were still large.

In 1996, Croatians who had developed techniques for fattening southern bluefin in Australia established the first Mediterranean tuna ranch, in the Adriatic. The process is simple. Newly caught bluefin are transferred to coastal sea cages, where—for months, even years—they are fed oily fish such as anchovies or sardines to give their flesh the high fat content so prized in Japan.