Correction to This Article
One of the headlines for a Nov. 3 article about endangered fish incorrectly described the conclusions. The researchers warned of the danger of the world's seafood supply running out, not of fish disappearing entirely.
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World's Fish Supply Running Out, Researchers Warn

"I think people don't get it," Lubchenco said. "They think, 'If there is a problem with the oceans, how come the case in my grocery store is so full?' There is a disconnect."

The possible collapse of commercial fisheries could have a serious on the global economy, said Gerald Leape, vice president for the advocacy group National Environmental Trust. The industry generates $80 billion a year, Leape said, and more than 200 million people depend directly or indirectly on fishing for their main source of income. Worldwide, a billion people eat seafood as their main source of animal protein.

"This should be a wake-up call to our leaders, both internationally and domestically, that they need to protect our fish stocks. Otherwise they will go away," Leape said.

In order to reach their conclusions, the paper's authors looked at nearly three dozen controlled experiments and crunched the U.N. Food and Agriculture Organization's worldwide catch data going back to 1950. In some cases, they also surveyed ecosystem records -- including sediment cores and archival data -- going back a thousand years.

The researchers said the loss of so many species is eroding the viability of marine ecosystems and their ability to resist environmental stresses. In 12 marine ecosystems surveyed, they found that a decline in biodiversity of 50 percent or more cut the number of viable fisheries by 33 percent, reduced nursery habitats by 69 percent and cut the ocean's capacity to filter and detoxify contaminants by 63 percent.

This phenomenon is apparent in the Chesapeake Bay, where the collapse of the oyster fishery has reverberated across the ecosystem. In 1880, there were enough oysters to filter all the water in the bay in three days; by 1988, it took more than a year for the remaining oysters to accomplish the same task.

Hunter Lenihan, a marine ecology professor at the University of California at Santa Barbara, said the mass dredging of oysters from the bay over the past century has transformed its ecosystem.

As the oysters declined, the water became more cloudy, and sea grass beds, which are dependent on light, died off and were replaced by phytoplankton that does not support the same range of species.

"When you removed the oysters through overfishing, that's when you begin to see a rapid decline in water quality," Lenihan said. "What it's done is change the entire production of the bay."

But University of Washington fisheries professor Ray Hilborn said ascribing a decline in fisheries production to loss of biodiversity was a bit like deciding which came first, the chicken or the egg.

"Do more productive systems lead to more diversity, or is it more diversity leads to more productivity?" Hilborn asked.

Yesterday's report suggests it is possible to resolve this puzzle. The researchers analyzed nearly 50 areas where restrictions had been imposed to stop overfishing and found that, on average, the range of species in the water increased by 23 percent within five years. That provides reason for optimism, Worm said, because it means sound management can halt the decline of fish stocks worldwide.

"It's not too late to turn this around," he said. "It can be done, but it has to be done soon."

Marine advocates, such as chief scientist Michael Hirschfield of Oceana, said they hope the report would spur countries to reassess their practice of providing roughly $20 billion a year in subsidies for harmful fishing practices.

"The single biggest thing we can do to address this is to eliminate subsidies," said Hirschfield, adding that European Union countries alone account for 10 percent of these subsidies.

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