Non-native oyster research

Due to dramatic declines in Chesapeake Bay native oyster populations (Crassostrea virginica), the states of Maryland and Virginia considered an introduction of a non-native oyster species, Crassostrea ariakensis, to their tidal waters including the Chesapeake Bay and Atlantic coastal bays. C. ariakensis appeared to be more resistant to the diseases that have devastated the native oyster population, and appeared to grow faster. C. ariakensis can grow much more quickly than does the native oyster. Some hoped that this Asian oyster would be able to revitalize the oyster industry and improve water quality in the Bay.

In response to the proposal by Maryland and Virginia to introduce reproductive C. ariakensis into the Chesapeake Bay, the U.S. Congress directed the U.S. Army Corps of Engineers, in cooperation with NOAA, the Environmental Protection Agency, and U.S. Fish and Wildlife Service, to prepare a programmatic Environmental Impact Statement (PEIS). Although the federal government was not directly involved in the plan to introduce C. ariakensis into the Bay, Congress deemed that the potential effects of an introduction were significant enough to require a PEIS.

Because at that time there was insufficient information to fully evaluate the effects the introduction of the Asian oyster might have on the Bay ecosystem, a summary of research needs was prepared by the Environmental Protection Agency, U.S. Fish and Wildlife Service, and NOAA to identify the largest gaps in knowledge about what effects an introduction of C. ariakensis might have. Federal resource agencies, environmental groups, and scientists concerned about the possible risks associated with a non-native introduction urged a cautious approach, including several years of focused research to answer key unanswered questions about the Asian oyster. Research funded by the NOAA Cheapeake Bay Office answered many of these questions.

In 2002, the Atlantic States Marine Fisheries Commission convened a workshop to review available information about potential risks and benefits of growing Asian oysters in Chesapeake Bay. In-water trials using triploid (sterile) Asian oysters had started at the Virginia Institute of Marine Science in 1998, and the researchers concluded that there were benefits from Asian oysters compared to native oysters. The Virginia Seafood Council had also conducted on-bottom trials in 2000 and 2001 using triploid oysters and did taste tests with the product, finding that it tasted similar to native oysters. But less information about potential risks from introduction of Asian oysters was available at the time.

In October 2002, the National Research Council and the Chesapeake Bay Program’s Scientific and Technical Advisory Committee (STAC) cosponsored a workshop on "Non-native Oysters in the Chesapeake Bay.” A publication resulting from the workshop recommended five to seven years of research in order to answer the most basic biological questions about C. ariakensis. In 2003 the Maryland Department of Natural Resources and the Potomac River Fisheries Commission began funding research on C. ariakensis. From 2004 through 2007, in response to Congressional direction, the NOAA Chesapeake Bay Office funded a non-native oyster research program for a total of $7 million in federal funds, with additional matching funds. The NOAA Chesapeake Bay Office-funded program was aimed at research priorities identified by the National Research Council and the STAC, as well as guidance from the International Code of Practice on the Introductions and Transfers of Marine Organisms.

Topics of this research included:

  • Understanding C. ariakensis taxonomy, pathogens, life history, and ecology within its native range
  • Interactions between C. ariakensis and the native oyster
  • Susceptibility of C. ariakensis to known disease-causing parasites and pathogens
  • Human consumption risk
  • Potential for population growth and sustainability of C. ariakensis in the Chesapeake Bay, especially in aquaculture
  • Potential for C. ariakensis to become a fouling nuisance
  • Economics and cultural impacts and ecosystem benefits of growing C. ariakensis

Research results were reviewed quarterly at meetings sponsored by the NOAA Chesapeake Bay Office. These quarterly review sessions facilitated timely discussions of research results among scientists and managers, and sped the transfer of information to the EIS evaluation process. Written summaries were prepared for each meeting. Results of the research were also shared at regular meetings of the Project Delivery Team for the EIS, and provided to the staff drafting the EIS. Results from many NOAA Chesapeake Bay Office-funded projects have also been presented at professional meetings and published in academic journals.

The NOAA Chesapeake Bay Office produced two IAN newsletters about C. ariakensis that summarized some of the issues and later some of the research findings. In 2009, the states of Maryland and Virginia and the U.S. Army Corps of Engineers jointly decided against a proposed introduction of Crassostrea ariakensis into the Chesapeake Bay. The PEIS recommended expanded efforts to restore native oysters. Many considerations went into the PEIS process. Possible risks and benefits that might have resulted from an introduction of Asian oysters were carefully considered.

One of the unexpected positive outcomes of this program involved triploid native oysters. In many projects done for the EIS, only triploid Asian oysters could be tested to reduce the risk of an accidental introduction, so the researchers started comparing them to triploid native oysters (rather than diploids, which were used at first) to make a more accurate comparison of growth rates, survival, and other parameters. The triploid native oysters performed well enough in some situations to make them an attractive option for aquaculture, in spite of their increased cost compared to diploids. Triploid native oysters now make up 91% of the oysters grown in aquaculture in Virginia, and are increasingly popular with Maryland growers. The EIS research also helped clarify the economics of oyster aquaculture using native oysters.