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Date: Aug. 14, 2003
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Foreign Oysters Not a Quick Fix for Chesapeake Bay, But Aquaculture of Sterile Oysters May Help

WASHINGTON -- Proposals to offset the dramatic decline of native oysters in the Chesapeake Bay by introducing a reproductive population of oysters from Asia should be delayed until more is known about the potential environmental risks, says a new report from the National Academies' National Research Council. In the meantime, however, carefully regulated aquaculture of sterile Asian oysters could help the oyster industry and generate information necessary for assessing some of the risks, said the committee that wrote the report.

"Introducing these non-native oysters in the Chesapeake Bay is not a magic bullet for either saving the oyster industry or restoring the bay," said Dennis Hedgecock, committee co-chair and a geneticist at the University of California, Davis. "It is unrealistic to expect that such action can reverse the long-term degradation of the bay in less than 10 years. But contained aquaculture of infertile non-native oysters on a small scale would provide more information for industry and policy-makers to make a sound decision on further use of non-native oysters."

Hit by decades of heavy fishing and disease, the native Chesapeake Bay oyster has been depleted to less than 1 percent of its peak abundance in the 1870s. As recently as 1980, the bay accounted for roughly 50 percent of the U.S. oyster harvest, but over the past decade, the region has produced only 1 percent to 5 percent of the total domestic supply of oysters. The price of Chesapeake oysters has declined by 24 percent in the last 10 years, and processors in both Virginia and Maryland now shuck and repackage oysters from the Gulf of Mexico and other regions outside the Chesapeake.

The state of Virginia has been studying the possibility of using non-native oysters since 1991, and began conducting field trials with the Suminoe oyster in 1996. But because of differing opinions among states and federal agencies about the environmental risks involved, the Chesapeake Bay Commission -- representing Maryland, Virginia, and Pennsylvania -- requested the National Research Council report.

The Suminoe oyster, which is native to coastal China and other Asian countries, is an appealing alternative to the native oyster because it is resistant to the two diseases that have reduced oyster populations up and down the East Coast. It grows quickly and compares favorably to the native oyster in taste tests.

But potential harmful effects of the Suminoe oyster on the ecology of the bay still need to be investigated, the committee said. Past introductions of foreign oysters in other parts of the world have brought diseases, parasites, and predators that have decimated native oyster populations. The report also notes that the Pacific oyster, another species from Asia which has been introduced around the world, has become invasive in parts of Australia and New Zealand, displacing the native rock oyster in some areas. Many of these threats can be reduced by using only sterile oysters grown in hatcheries that follow strict international guidelines, according to the committee.

Several issues require further research, the report says, including the potential introduction of a new disease, competition with native oysters, dispersal of non-native oysters outside the Chesapeake Bay, and market demand for non-native oysters. This additional research will be needed before scientists can reassess the environmental risks of wider aquaculture of sterile non-native oysters or the introduction of reproductive ones.

"There is concern that non-native oysters could become another obstacle to native oyster restoration without providing significant relief to the oyster industry," said committee co-chair Jim Anderson, a fisheries economist at the University of Rhode Island, Kingston. "Confined aquaculture of non-native oysters will provide much-needed information, while allowing more time for recovery of the native oysters."

Restoring the native Chesapeake Bay oyster is still a real possibility, the committee pointed out. It noted, for example, that oysters in the Delaware Bay have developed resistance to one of the diseases that is currently killing the Chesapeake oysters.

The committee was asked to consider three management options: prohibiting the use of non-native oysters altogether; growing infertile non-native oysters in a contained aquaculture setting; or establishing a reproductive population of non-native oysters in the bay. It concluded that the contained aquaculture of sterile oysters offers an interim approach, while a deliberate introduction of reproductive oysters would likely be irreversible and could affect native species not only in the Chesapeake but also in other Atlantic coastal regions and the Gulf of Mexico. Controlled aquaculture also offers -- at least when conducted on a small scale -- more opportunity for adapting management decisions to changing circumstances, while giving scientists time to further study how the non-native oyster interacts with the bay's ecosystem. And it makes an unregulated, rogue introduction less likely than if non-native oysters were not allowed at all.

Because the method used to produce sterile oysters is not 100 percent effective, watermen and local officials must try to prevent the escape of any reproductive non-native oysters, the committee warned. Sterile oysters are called triploids because they contain three sets of chromosomes instead of the normal two, and this extra set prevents reproduction. But the technique used to generate triploids fails in about one out of every 1,000 oysters, and even triploid oysters may become reproductive after several years, the committee noted. It said the risk of reproductive non-native oysters getting into the bay can be reduced if triploid oysters are harvested before they reach reproductive age.

In addition, regulatory standards aimed at minimizing any unintentional release of reproductive non-native oysters need to be established before any further pilot tests or aquaculture of triploid oysters proceeds, the committee said. Legal authority to regulate the introduction of non-native species could be given to the Chesapeake Bay Program, a regional federal-state partnership that has already spent considerable time scrutinizing the proposal to introduce Suminoe oysters. Since the federal government does not regulate the introduction of most non-native species, similar partnerships are needed in other parts of the country, the committee added. The report was sponsored by the U.S. Environmental Protection Agency, National
Oceanic and Atmospheric Administration, U.S. Fish and Wildlife Service, Maryland Department of Natural Resources, Virginia Department of Environmental Quality, Virginia Sea Grant, Maryland Sea Grant, Connecticut Sea Grant, and the National Fish and Wildlife Foundation. The National Research Council is the principal operating arm of the National Academy of Sciences and the National Academy of Engineering. It is a private, nonprofit institution that provides science and technology advice under a congressional charter. A committee roster follows.
Copies of Study on Non-Native Oysters in the Chesapeake Bay will be available this fall from the National Academies Press; tel. 202-334-3313 or 1-800-624-6242 or on the Internet at Reporters may obtain a pre-publication copy from the Office of News and Public Information (contacts listed above).

Division on Earth and Life Studies
Ocean Studies Board

Committee on Non-Native Oysters in the Chesapeake Bay

James L. Anderson (co-chair)
Professor and Chair
Department of Environmental and Natural Resource Economics
University of Rhode Island

Dennis Hedgecock (co-chair)
Bodega Marine Laboratory
University of California

Mark Berrigan
Bureau of Aquaculture Development
Florida Department of Agriculture and Consumer Services

Keith Criddle
Professor and Head
Department of Economics
Utah State University

Bill Dewey
Division Manager
Project Development and Public Affairs
Taylor Shellfish Company Inc.
Shelton, Wash.

Susan Ford
Research Professor
Department of Marine and Coastal Sciences
Rutgers University
New Brunswick, N.J.

Philippe Goulletquer
Laboratory of Shellfish Genetics and Pathology
French Research Institute for Exploitation of the Sea

Richard G. Hildreth
Professor and Co-director
Ocean and Coastal Law Center
School of Law
University of Oregon

Michael Paolisso
Associate Professor
Department of Anthropology
University of Maryland
College Park

Nancy Targett
Graduate College of Marine Studies
University of Delaware

Robert Whitlatch
Department of Marine Sciences
University of Connecticut


Susan Roberts
Study Director