Giant bluefin tuna, which can grow as large as 1,500 = pounds in the wild, are studied at the Monterey Bay Aquarium, the only facility in= North America where these fish are held in captivit= y for exhibit and research. (Randy Wilder, Monterey Bay Aquarium ) &nbs= p; &= nbsp; &nbs= p; =

Advocates Hope Science Can Save a Big Tuna

By J= uliet Eilperin

Washington<= /span> Post Staff Writer
Monday, December 24, 2007; Page A06

For centuries, humans have mythologized the <= span class=3DSpellE>bluefin tuna, an elite, warmblooded fish that can traverse the Atlantic basin= in less than a month and a half and grow to weigh three-quarters of a ton. Rom= ans put bluefin on their coins; Salvador Dali painted them.

Now, researchers are using hard science to pr= event the fish from going extinct.

Analyzing facets including chemical markers i= n the tuna's ear bones and satellite readings generated by tags attached to migra= ting fish, marine biologists are beginning to decipher how separate bluefin populations travel and spawn. And those distinctions, they say, may help determine whether fishery managers can preserve the Atlantic's remaining giant = tuna.

"We know phenomenally more about bluefin now than we did 15 years ago. We know enough = to save this species," said Michael Sutton, vice president and director of the Center for the Future of the Oceans at Monterey Bay Aquarium in California. &quo= t;We don't have the will."

As demand for the tasty fish has soared among= sushi connoisseurs -- and as Americans and Europeans face off over who bears the = most responsibility for plummeting Atlantic bluefin = stocks -- scientists have helped answer one of the key questions now confronting fishery managers: Two separate populations of bluefin<= /span> swim in the Atlantic basin. In other words, humans cannot afford to let eit= her stock disappear completely, because they are genetically distinct.

For years, Europeans have been overfishing bluefin tuna that breed in the Mediterranean. In fact, for the past four years European Union officials have set catch qu= otas at nearly double the levels their scientists recommended, and fishermen have exceeded those already-elevated quotas by 50 percent each year. In the United States, the federal government has = imposed greater restrictions, but fishermen can still bring home bluefin tuna they incidentally catch as the fish are spawning each spring in the Gulf of Mexico.

"We have some excellent science," s= aid John Graves, a professor at the Virginia Institute of Marine Science who studies bluefin by conducting DNA analysis. &qu= ot;The real challenge here is to get the science translated into management, and that's where we're hitting a roadblock."

The fact that bluefin from the Mediterranean and those from the Gulf of Mexico mix most of the ye= ar has led some fishermen to think the stock off America's East Coast has been faring better than it actually is, Graves said. Instead, he added, fishery managers need to realize that western Atlantic= bluefin off the East Coast are in dire shape. There a= re two other species of bluefin, Pacific and southern,= which face their own fishing pressures.

"What you have now are essentially two s= tocks, but the only time the stocks are separated is during spawning," Graves said, adding that the two Atlantic populatio= ns do not interbreed. "We need to protect the western stock, because that's a unique genetic entity."

For years, researchers knew little about how pelagic fish such as bluefin travel, feed and mate. But new developments have allowed scientists to better understand a species that can fetch more than $170,000 for a single fish. <= /p>

"It's the Porsche of the ocean," sa= id Sutton, whose aquarium keeps bluefins in its Outer Bay exhibit. "It's as fast as a sports car, it weighs as much as a sports = car and it's as valuable as a sports car."

Satellite tags -- which c= an record the temperature of the ocean as well as the depth at which the fish = swim and the level of light to which they are exposed -- have provided scientists with a precise record of how bluefin tuna trave= l. Stanford University marine biologist Barbara A. Block and her colleagues tagged two fish within= a matter of minutes off western Ireland; within eight months, the fish were more than 3,000 miles apart. One had traveled to waters just northeast of Cuba; the other swam off the coast of Portugal.

Block's team has used a different kind of electronic tag, which they surgically implant in bluef= in tuna, to record at regular intervals not only where the tuna go but how the= ir bodies react to the surrounding environment. This year, a student of Block'= s, Steve Teo, published a paper chronicling that t= he tuna warm as they engage in courtship, and tend to stay in warmer waters su= ch as the Gulf of Mexico during this period= .

Jay R. Rooker, a = marine biologist at Texas A&M University, has used a different technique to reach the same conclusions as Graves and Block. Rooker and his colleagues examine otoliths, or ear bones, = of bluefin to determine where the fish originate and jou= rney, because the chemical composition of these ear bones reflects the water in w= hich the fish have been swimming. By reading the isotopes of carbon and oxygen contained in these ear bones, Rooker can isolat= e bluefin from the Mediterranean and the western Atlantic.

"If you look at them over many years, th= ey do look different," Rooker said.

The discovery that the two stocks are genetic= ally different has prompted the realization that the number of western-stock bluefin that U.S. fishermen are catching is inflated by migrants from the Mediterranean. These findings have prompted several scientists and conservationists to cal= l on the National Marine Fisheries Service (NMFS) to shut down longline fishing in the Gulf of Mexico between Ap= ril and June while bluefin tuna are spawning there. Federal officials have resisted these calls and are fighting a lawsuit on t= he issue filed here in federal district court by Earthjus= tice on behalf of the advocacy group Blue Ocean Institute and its president, Car= l Safina.

NMFS Director William T. Hogarth agrees that bluefin tuna are in trouble off the= East Coast. "We're catching nothing," he said, noting that U.S. fi= shermen have collected less than 15 percent of their official catch quotas for the = past five years.

But he has devoted most of his energy to pres= sing the Europeans to cut back on bluefin catches, something they have steadfastly refused to do. "It's totally out of control," Hogarth said, adding that when it comes to halting fishing in the Gulf of Mexico, "If the science tells = us that is what it's going to take to recover bluefin tuna, then the federal government will consider it and probably do it."= ;

Safina, speaking = by telephone as he conducted research in Belize, said the science was already settled.

"To say there's not enough science to te= ll us whether we need to protect the last few fish that are trying to breed on our side of the ocean, that is just nonsensical," he said. "I believe that is illegal. The law requires better stewardship than [government officials] sitting on their hands and doing nothing."

Staff researcher Magd= a Jean-Louis contributed to this report.