Consensus Report

Nonnative Oysters in the Chesapeake Bay (2004)


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The native oyster species of the Chesapeake Bay has been depleted to less than one percent of its original population. As a result, the Chesapeake Bay states are looking for ways to revive the oyster industry. This report discusses the proposed plan to offset the dramatic decline of the Chesapeake Bay's native oysters by introducing disease-resistant, reproductive Suminoe oysters from Asia. It is recommended that the introduction be delayed until more is known about the environmental risks, even though carefully regulated cultivation of sterile Asian oysters in contained areas could help the local industry and researchers. It is also noted that even though oysters also consume some of the excess algae caused by pollution, it could take decades before there are enough of them to improve water quality.

Key Messages

  • Although Option 1 is reversible in the sense that nonnative oysters could still be introduced at some time in the future, this option includes the risk of continued losses to the oyster industry and erosion of confidence in government action. One possible response to the latter is increased risk of a rogue introduction and the especially high hazards associated with unintentional cointroductions of disease organisms or nuisance species.
  • Because of the lack of information on the biology and ecology of the Suminoe oyster, there is a high degree of uncertainty about the outcome of an introduction.
  • If regulators enforce strict protocols for accountability and require collection of the biological, economic, and social information necessary to evaluate the risks and benefits of culturing or introducing the nonnative oyster, this management option could provide useful information to support decision analyses and risk assessments regarding the future use of nonnative oysters in the Chesapeake Bay.
  • It is impossible, given the present state of knowledge, to predict whether the Suminoe oyster will be a boon or an ecological disaster in this sense.
  • On the basis of existing information about oysters in general and the Suminoe oyster in particular, Option 3 direct introduction of reproductive Suminoe oysters would likely have a moderate to high chance of increasing the abundance of oysters in the Chesapeake Bay, particularly if it was done as a massive introduction, much as the Pacific oyster was introduced into France. To the extent that the introduction was successful, this action might reduce the likelihood of a rogue introduction.
  • Option 1 no use of nonnative oysters is unlikely to result in significant changes in oyster abundance in the bay in the near term. This outcome has moderate uncertainty, owing to external events or actions that might favor the recovery of native oyster populations (e.g., favorable climate change or success in restoration efforts employing selectively bred, disease-resistant stocks).
  • Option 2 has already received considerable scrutiny by the Chesapeake Bay Program and its member states and federal agencies. Limited field trials with triploid nonnative oysters have already been conducted in Virginia and outside the bay in North Carolina's coastal waters, and larger trials are in the advanced planning stages in both states. To a limited extent, the decision to introduce triploid Suminoe oysters has already been made.
  • Option 2 sterile triploid aquaculture carried out with strict accountability and best management practices to minimize the risk of diploid escape would probably have little impact on total oyster abundance because even expanded aquaculture operations are unlikely to produce a volume of oysters at the scale of the natural populations in the Bay. Uncertainty associated with this action would be low.
  • Regulatory and enforcement measures should be taken to reduce the risk of a rogue introduction.
  • The committee concluded that quantitative risk assessments could not be conducted based on existing data but found that differences in the types of risks associated with each option could be described.
  • The committee's review of case studies clearly indicates that greater ecological or economic harm typically arises from organisms that are inadvertently introduced with the foreign oyster.
  • The existing regulatory and institutional framework was found to be inadequate for monitoring or overseeing the interjurisdictional aspects of open-water aquaculture or direct introduction of C. ariakensis.
  • The irreversibility of introducing a reproductive nonnative oyster and the high level of uncertainty with regard to potential ecological hazards make Option 3 an imprudent course of action.
  • The risks of proceeding with triploid aquaculture in a responsible manner, using best management practices, are low relative to some of the risks posed under the other management options.