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Advocates Hope Science Can Save a Big Tuna

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 captivity for exhibit and research.
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 captivity for exhibit and research. (Randy Wilder, Monterey Bay Aquarium )

Block's team has used a different kind of electronic tag, which they surgically implant in bluefin tuna, to record at regular intervals not only where the tuna go but how their bodies react to the surrounding environment. This year, a student of Block's, Steve Teo, published a paper chronicling that the tuna warm as they engage in courtship, and tend to stay in warmer waters such 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 journey, because the chemical composition of these ear bones reflects the water in which the fish have been swimming. By reading the isotopes of carbon and oxygen contained in these ear bones, Rooker can isolate bluefin from the Mediterranean and the western Atlantic.

"If you look at them over many years, they do look different," Rooker said.

The discovery that the two stocks are genetically 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 call on the National Marine Fisheries Service (NMFS) to shut down longline fishing in the Gulf of Mexico between April and June while bluefin tuna are spawning there. Federal officials have resisted these calls and are fighting a lawsuit on the issue filed here in federal district court by Earthjustice on behalf of the advocacy group Blue Ocean Institute and its president, Carl 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. fishermen 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 pressing 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 tell 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 Magda Jean-Louis contributed to this report.


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