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Fall 2003 Vol. 3 No. 3

Table of Contents

Hatchery grown seed oysters ready for placement to restore an oyster reef in the Chesapeake Bay; photo courtesy National Oceanic and Atmospheric Administration

From the
Far East
to the
Eastern Shore

Will Asian Oysters Help or Harm Chesapeake Bay?

Oysters were once so abundant in Chesapeake Bay that ships found it hard to navigate around the huge oyster reefs that filled the waters. For hundreds of years, Chesapeake residents -- both human and animal -- benefited from this bounty. The oysters' plentiful numbers and natural filtering ability helped keep the waters clear, and thousands of watermen made a living fishing for oysters. The Chesapeake oyster industry provided jobs to many in bay communities, shipping catches to markets and restaurants around the country. As recently as 1980, in fact, the Chesapeake yielded about half of the U.S. oyster harvest.

But today the oysters you encounter at a raw bar or at the supermarket are far more likely to come from the Gulf of Mexico or the Pacific Northwest than the Chesapeake. Decimated by parasitic diseases, overfishing, and a decline in water quality, Chesapeake oysters now make up no more than 5 percent of the U.S. harvest.

As the oysters have dwindled, so have the fortunes of the watermen and communities who depend on them. States, private organizations, and the EPA have recently launched efforts aimed at restoring the population of native oysters. But the urgency of the watermen's economic plight has prompted industry groups to push for a more radical approach -- introducing the Asian Suminoe oyster into the Chesapeake.

Supporters of the plan hope that the Asian newcomers, which are resistant to the diseases killing the native oyster, will thrive in the bay and revive the industry. But the danger -- always present when a new species is introduced into an ecosystem -- is that the oysters could instead become a pest, clinging to boats and docks and possibly displacing native species. And the consequences could ripple beyond the bay; Asian oysters could be transported throughout the Atlantic coast and Gulf of Mexico, threatening productive oyster fisheries in other regions.

Several state and federal agencies asked the National Research Council to assess the risks and benefits of introducing the Asian oysters either by raising sterile oysters in a controlled setting -- a method currently being pursued in Virginia -- or as a reproductive population in the wild, the alternative favored by Maryland.

Oysterman; photo by Golden Memories Studio Inc.

Introducing breeding oysters into the bay would be unwise now, the Research Council's report concludes, given that little is known about the potential consequences and that this step would be irreversible. But doing nothing has its dangers too, said the committee that wrote the report. Desperation among watermen -- which may increase if the government fails to act -- could provoke an unauthorized or "rogue" introduction of oysters, which poses the greatest threat to the bay's ecosystem. If proper protocols aren't followed, diseases and undesirable marine creatures would likely hitchhike into the bay along with the oysters.

As for large-scale aquaculture, the committee cautioned that the process used to generate sterile oysters is not failsafe. One in every 1,000 oysters produced is likely to be a normal reproductive oyster, and even some of the sterile oysters may become capable of breeding, if allowed to grow for many years.

Still, raising the oysters in this type of controlled setting is the best option of the alternatives under consideration, the committee concluded. Following strict standards for confining and monitoring the oysters would minimize the odds that breeding oysters would be released into the bay. And not only would oyster "farming" create employment opportunities in the bay area, it may also give the native oyster time to recover.

Most important, this option will give scientists a chance to study how the Asian oysters behave in bay waters. With several years of research, scientists will be better able to predict whether, if released to breed in the wild, the Asian oyster would be the Chesapeake's friend or foe.   -- Sara Frueh

Non-Native Oysters in the Chesapeake Bay. Committee on Non-Native Oysters in the Chesapeake Bay, Ocean Studies Board, Division on Earth and Life Studies (2003, approx. 250 pp.; ISBN 0-309-09052-0; available from the National Academies Press, tel. 1-800-624-6242; $36.00 plus $4.50 shipping for single copies).

The committee was co-chaired by James Anderson, professor, department of environmental and natural resource economics, University of Rhode Island, Kingston; and Dennis Hedgecock, professor, Bodega Marine Laboratory, University of California, Davis. The project 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, Maryland Sea Grant, Virginia Sea Grant, Connecticut Sea Grant, and the National Fish and Wildlife Foundation; a contribution was made by the Scientific and Technical Advisory Committee of the Chesapeake Bay Program.

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Copyright 2003 by the National Academy of Sciences