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Background
In hopes of reversing declining populations of native oysters, the Bay states and the federal government are working with researchers to develop innovative restoration programs aimed at returning abundant native oyster populations to the Bay. As recently as July 2003, Bay Program partners re-affirmed their Chesapeake 2000 commitment to a ten-fold increase in the number of restore native oysters in the Bay. While most of the historic decline of Chesapeake Bay oyster population is attributed to habitat degradation and overharvest, two diseases - Dermo and MSX - are considered the modern leading cause of native oyster mortality. Dermo and MSX were first discovered in the Eastern oyster, Crassostrea virginica, in the 1950s. While the effects of MSX and Dermo are most acute in higher salinity waters found in the lower portion of the Bay, both diseases have expanded into less saline waters further up the Bay. Scientists believe MSX was inadvertently introduced to the Chesapeake through the importation of a non-native oyster, Crassostrea gigas, in the 1930s. While Chesapeake Bay Program partners continue their work to restore native oysters, efforts are also underway to better understand the risks and benefits surrounding the possible introduction of non-native oysters into the Bay. Introducing Non-Native Oysters into the Bay In hopes of reestablishing a Virginia commercial oyster industry, in 1995, the Virginia legislature directed the Virginia Institute of Marine Science (VIMS) to begin a study on non-native oyster species for possible introduction to the Chesapeake Bay.VIMS first studied C. gigas, a popular and widely cultivated non-native oyster. The studies used oysters in a triploid, or non-reproductive, form. The C. gigas results were unimpressive, showing inferior growth and survival in lower salinities compared to the native oyster. Through an Environmental Impact Statement, the U.S. Army Corps of Engineers are now leading an evaluation of a proposal by the states of Maryland and Virginia to introduce the Asian oyster species, Crassostrea ariakensis, into the tidal waters of the Chesapeake Bay. The Environmental Impact Statement will also evaluate alternatives to this proposal. The states and the Corps will continue native oyster restoration efforts throughout the Chesapeake Bay. Introducing Ariakenis, the Suminoe Oyster
As of July 2004, approximately 860,000 triploid Suminoe oysters have been tested in the Bay. The Virginia Seafood Council has received permits to conduct industry trials with triploid Suminoe oysters. Due to the possibility of oysters reverting to diploid, or reproductive form and the reality that all triploid stocks include some diploids, some scientists and mangers are concerned that the industry trials could result in establishing a free-living reproductive Suminoe population in the Bay. Such a non-native introduction could be an irreversible action, and some are concerned that it could significantly affect the health of the Bay ecosystem. Because of this concern, federal and state permits for the Virginia Seafood Council trials imposed strict bio-security and monitoring requirements. What’s at Stake? Within the Bay community, there is an ongoing debate among those supporting immediate ariakensis introduction and those advocating further research before making a decision about introducing the species to the Bay. Some stakeholders, including the Virginia Seafood Council and some Maryland and Virginia watermen, view the Suminoe oyster as a promising solution to several problems, and strongly urge widespread introduction of sterile – or possibly even fertile – Suminoe oysters. Their view is that the Suminoe oyster could serve to revitalize the industry as well as provide the means for improved water quality through increased bio-filtration. Other potential benefits include a reduction of fishing pressure on the native oyster and the creation of hard substrate for further oyster attachment and reef development. Other stakeholders believe that a non-native species introduction needs to be approached with a high level of caution. Many are concerned about the species' disease-harboring capabilities including possible pathogens that could harm native populations of aquatic plants and animals. Others are concerned about food web effects that could alter benthic communities and ecosystems, while competition and reproductive interference with the native oyster may create additional pressures on already low virginica populations. The National Research Council Study In 2003, the National Research Council of the National Academy of Sciences completed a year-long study to evaluate whether enough is known about the biology of C. ariakensis to effectively assess these benefits or risks at this time. The study represents the most complete analysis to date of available literature and science pertaining to the possible introduction of non-native oysters into Chesapeake Bay. It will serve as the basis for both near- and long-term management strategies affecting the future of non-native oysters in the Chesapeake. Its findings will guide new research, establish risk assessment needs and form a significant component of Environmental Impact Statement regarding the possible introduction of the Suminoe oyster.
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Once
researchers determined C. gigas unsuitable for Bay waters, efforts began
to focus on an Asian Suminoe oyster, C. ariakensis. In limited field
trials, the Suminoe oyster demonstrated lower mortality from Dermo and
MSX, hearty and rapid growth, and success in taste tests. Researchers
found Suminoe oysters grow to market size in only nine months as opposed
to two years for the native virginica. This has resulted in increased
pressure from the seafood industry to adopt the non-native alternative.
