expect that this long-term degradation in the Chesapeake Bay could be reversed in 10 years or less through any single management action. The degradation of water quality, increased sedimentation, loss of habitats such as sea grass beds and oyster reefs, and changes in the abundances of many plant and animal species not only serve as indicators of change but also act as barriers to restoration. Improvements in the natural resources of the bay will require a multifaceted approach and sustained commitment from communities throughout the watershed toward the goal of reestablishing some of the ecological functions that have been valued for generations.

Loss of the Native Oyster

The indigenous oyster C. virginica has been depleted to less than 1% of its original abundance in the Chesapeake Bay through a combination of heavy fishing pressure during the 19th and 20th centuries and the recent high mortalities due to the spread of two parasites, Haplosporidium nelsoni and Perkinsus marinus, that cause the diseases MSX and Dermo, respectively. Additionally, nutrient and toxic pollutants, increased sedimentation, and loss of shell bed habitat have made the environment in the bay less conducive to recovery of the oyster population. This combination of factors has threatened the survival of the oyster industry in Virginia and Maryland. As a possible means to address this problem, Virginia has been exploring the option of introducing a nonnative Asian oyster (C. ariakensis) into the state’s coastal waters, including the Chesapeake Bay.

Opinions on the likely risks and benefits of introducing a nonnative oyster differ among the states and federal agencies that participate in regional agreements through the Chesapeake Bay Program (CBP). Because of the high stakes associated with the decision to introduce a nonnative species, the Chesapeake Bay Commission (a tristate commission that serves as the legislative arm of the CBP) requested that the National Research Council undertake a study of the pros and cons of introducing C. ariakensis either as an infertile triploid (triploid oysters contain three rather than the normal two sets of chromosomes and cannot reproduce normally) for use in aquaculture or as a reproductive diploid that could either augment or supplant the diseased populations of the native oyster (see Box 1.1). In the past, introductions of nonnative species were not subjected to this level of scrutiny, but rising awareness of the potential ecological and economic problems associated with invasive nonnative species has made resource managers more cautious. Thus, this study presents a landmark opportunity to identify concerns that should be addressed by decision makers when the introduction of a nonnative marine species is under consideration.



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