Shark numbers decline sharply


Published: Friday, January 17, 2003 at 6:01 a.m.
Last Modified: Friday, January 17, 2003 at 12:30 a.m.
Shark populations in the northwest Atlantic Ocean have plunged by more than half since scientists began keeping careful track in 1986, with species such as the hammerhead and the great white falling more than 75 percent, researchers said.
Such an abrupt decline in the ocean's dominant hunters could substantially alter marine food chains in ways that are impossible to predict and might take decades to reverse, the researchers and other experts said.
The researchers, from Dalhousie University in Halifax, Nova Scotia, ascribed the drop to intensifying commercial and recreational fishing for sharks, which reproduce slowly compared with other oceanic fish. They are describing their findings today in the journal Science.
The Dalhousie researchers, led by Julia K. Baum, a doctoral candidate at the university, said similar declines had probably occurred elsewhere and that "pervasive overfishing of these species may initiate major ecological changes."
They said there was no evidence that the decline was the result of any natural cycle.
Other biologists had reported declines in particular coastal areas, but several experts not involved in the new study said the research provided the first detailed overview of an oceanwide decline with broad implications.
The effects on other marine life, shark prey and other predators, remain unknown, but could last for generations, experts said.
"It's a giant experiment, and we're not just playing in the laboratory here," said Dr. Robert E. Hueter, the director of the Center for Shark Research at the Mote Marine Laboratory in Sarasota. "We're playing with the future of our marine food resources."

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