MADRID — Bluefin tuna, a favorite of sushi lovers, graces dinner tables from Japan to the United States. But because the waters off these countries hold an insufficient bounty of the delicacy, fishermen use the overfished and under-regulated Mediterranean to satisfy demand.

With the season opening April 15, south European and North African fisheries are gearing up for another year in hot pursuit of one of the world’s prize catches.

Yet the traditional disregard for quotas leaves fishermen and consumers alike wondering how devastating the damage from overfishing will be this year.

“The industry has to show it can control itself," said Maria Jose Cornax, a marine biologist at the conservation group Oceana. "It is overexploiting a species in a delicate equilibrium and in danger of commercial collapse."

And the zeal looks to threaten more than just the Mediterranean tuna population.

The bluefin stock on the Eastern seaboard and in the Gulf of Mexico has been unable to recover from overfishing despite more than a decade of strict regulations. Studies on migration patterns suggest that the failure to replenish that stock derives at least in part from depletion in the Mediterranean.

That connection has led many to push for a truly Atlantic solution to save the fishery. But scientists are still unsure how much mixing occurs between the different populations and the hunting frenzy seems unlikely to recede in the absence of more conclusive research.

Scientists do not think the Atlantic and Mediterranean populations interbreed, but they do share common feeding ground in the north Atlantic.

Lobbying by U.S. fisheries for increased restrictions in the Mediterranean and east Atlantic waters has been met with firm resistance in the coastal countries that profit most from selling their catch to the highly developed sushi-sashimi market of Japan.

In its 2008 stock assessment, the International Commission for the Conservation of Atlantic Tunas (ICCAT) estimated that the 2007 haul by European and North African fisheries may have doubled the quota agreed to by ICCAT member nations, including the United States and European Community. The total was at least three times more than ICCAT scientists recommended for sustainability.

Watchdog groups point to Mediterranean countries — and particularly Spain— as major culprits in depleting the eastern Atlantic tuna. The global conservation group WWF said Italy, Algeria and Libya all had too many boats equipped for bluefin tuna fishing. It also said that catches have been seriously underreported in recent years, specifically pointing to Spain and Croatia.

The fishing of Atlantic bluefin tuna in the Mediterranean Sea dates back millennia. But the nickname "Giant" for the bluefin — which can reach heights double the size of a man — is more of a misnomer these days, when the average catch size is about half that.

Japanese businessmen revolutionized the Mediterranean industry a decade ago when they invested in a troubled Spanish fishing fleet and introduced the use of tuna fattening pens at sea.

The pens encourage fishermen to haul in many more and smaller bluefin during the limited fishing season. The technique allows them to fatten up the tuna to minimum catch size while in the pens and to sell the tuna fresh from the pens year-round for top dollar.

For years afterward the Spanish led the capture of bluefin tuna in the Mediterranean and capitalized on their knowledge by exporting the model across much of the Mediterranean. As a result, the fishing fleet largely responsible for filling the tuna pens grew nearly 40 percent from 1997 to 2008, and it accounted for more than half of the bluefin catch, according to a 2008 report from WWF.

Cornax said the challenges of compliance and regulation that have plagued the fishery since it modernized in the mid-1990s remain unresolved.

Blatant abuses of bluefin fishing restrictions prompted the European Union to end the season in its waters a couple of weeks early last year. Cornax said a European Union initiative adopted in March to heighten controls through rigorous inspections comes too late and is unrealistic.

“The measures seem adequate on paper. But not even the EU can guarantee 100 percent inspection in the Mediterranean. There aren’t enough inspectors. There are too many illegal ports,” she said.

What’s more, Cornax points to the strategic move of European fleets to Mediterranean waters outside the European Union during last year’s early closure. She said a comprehensive quota agreement respected by all involved parties is essential.

But at the current capture rate, “even ensuring 100 percent compliance is insufficient,” she said. “That’s no way to recover the species.”

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