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Friday, October 10, 2008

Asian Oyster Holds Promise, Risk

Species could re-establish depleted bay fishery, study says
By Timothy B. Wheeler

State officials say they want to hear public views on the Asian oyster. Some environmentalists fear decisions will be based on politics, not science.

Photo courtesy of Virginia Institute of Marine Science

Seeding the Chesapeake Bay with disease-resistant Asian oysters could significantly boost the bay's depleted population of the water-cleaning shellfish, according to a federal study to be released next week.

But the study, a copy of which was obtained by The Baltimore Sun, warns that the foreign species also could harm what's left of the bay's native oyster population - and perhaps spread to threaten ecosystems all along the East Coast.

The draft environmental impact statement by the Army Corps of Engineers lists pros and cons of the controversial proposal to put Asian oysters in the bay, an idea that had been pushed hard by the Ehrlich administration to revive a flagging seafood industry.

But after more than four years of research and debate among scientists, the $17 million study does not make a recommendation about what route would be best for the bay. Officials say they want to hear public views on the matter first.

That stance bothers some environmentalists, who say the decision should be based on science - not a political desire to help the seafood industry.

Jamie King, a former federal scientist who coordinated much of the research that went into the study, called the lack of a recommendation "an abdication of responsibility." She said state and federal agencies had pledged to base their decision on science, but she suspects they will rely on "the court of public opinion."

"They want to see who screams the loudest," she said.

But an O'Malley administration official said restoring the bay's oyster population is a public policy issue that goes beyond science.

"It's not going to be put to a vote, but we're very interested in hearing the public's feedback on the options before us," said Tom O'Connell, fisheries director for the Maryland Department of Natural Resources. O'Connell said officials want to know how committed people are to restoring the native oyster, and how willing they are to take a chance on an Asian oyster that could cause other problems.

The study, funded by Maryland, Virginia and federal agencies, was launched four years ago to settle a growing debate about the environmental risks of putting non-native oysters in the bay to supplement a native oyster population decimated by parasitic diseases and overharvesting.

The O'Malley administration, unlike Ehrlich's, is "skeptical" about the wisdom of introducing Asian oyster, O'Connell said. After six public meetings over the next two months, the two states and the Army Corps hope to agree early next year on whether to introduce Asian oysters, continue working to restore native oysters, or both.

Oysters are seen by many as a key to the bay's health. Scientists have suggested that the bay's water-quality woes may be linked in part to the drastic decline in bay oysters, since by some estimates they were once so abundant they filtered all the Chesapeake's water every three or four days.

Efforts to restore the native oyster by propagating millions of them in government hatcheries have produced only mixed results to date - though critics point out that in Maryland, watermen are still allowed to harvest many of the publicly produced oysters.

Urged on by its seafood industry, Virginia has been growing sterilized batches of the Asian oyster in its portion of the bay for years to see how they fare. Seafood processors and watermen in both states argue that their livelihood is doomed without a new oyster capable of fending off the parasitic diseases that kill native oysters before they can grow large enough to market.

The study looks not only at seeding the bay with billions of Asian oysters, but at growing sterilized Asian oysters in the bay for commercial use. It also evaluates several options for stepping up efforts to restore native oysters - including a baywide moratorium on harvesting them.

It found that doing everything at once - introducing sterile and reproducing Asian oysters, and boosting native oyster work - offers the best prospects for rebuilding an oyster population in the bay. But that approach also carries the greatest risks of environmental harm, the study warned, and it still may not succeed at restoring oysters to the abundance they had until about 40 years ago.

"I think there's some serious promise" with the Asian oyster, said Kennedy Paynter, a University of Maryland oyster biologist who has worked with both species. "But I think that the potential for serious negative impact that we don't understand yet is still quite high."

Asian oysters have proven fast-growing and resistant to the two parasitic diseases killing native bay oysters. But research in recent years has found that the imports are more vulnerable to predators and poor water quality. They die off relatively quickly when oxygen levels drop in the water - a serious issue, some scientists say, because of the "dead zone" that spreads across the bay bottom in summer.

They also seem to be vulnerable to another parasite than the ones killing native oysters. A batch of Asian oysters being tested in North Carolina died off after becoming infected with Bonamia, an organism not seen in the bay now but capable of surviving in its saltier waters.

If Asian oysters do take hold in the bay, the study says, research has shown that they may compete with native oysters for food and habitat, raising concerns that the import could crowd out the native.

Seafood industry leaders have indicated they'd like to practice aquaculture with sterile Asian oysters, which would grow especially fast and large. But scientists have warned that reproducing Asian oysters could eventually end up in the bay, and then spread. The study says that if that happened, it would take many years.

"That's the ultimate question: How much risk are you willing to accept?" said Jack Travelstead, fisheries director for the Virginia Marine Resources Commission.

Stan Allen, an oyster researcher at the Virginia Institute of Marine Science, argues that the risks of using sterile Asian oysters are manageable, and that any escape of reproducing oysters could be detected and cleaned up before they could spread. He suggested that risk ought to be weighed against the prospect of reviving the region's struggling oyster industry.

Other scientists and environmentalists urge caution.

"The burden of proof needs to be on the [advocates of ] introduction to show that it will not result in significant problems," said William Goldsborough, senior scientist for the Chesapeake Bay Foundation.

"If the Asian oyster is introduced successfully to Chesapeake Bay, that's an irreversible decision ... that still has very uncertain consequences, in terms of risk and benefits," said Denise Breitburg, senior scientist at the Smithsonian Environmental Research Center in Edgewater.

"Given that," she said, "we should exhaust all possibilities for native oyster restoration before we do what I consider a drastic step."

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