The U.S. Fish and Wildlife Service has called for a moratorium on any further work with nonnative Crassostrea ariakensis oysters in the Chesapeake, citing the lack of information about its potential risks to the Bay.

The letter, sent by Mamie Parker, director of the service’s Northeast Region which includes the Bay states, is at odds with a resolution passed by the Virginia General Assembly that encourages further work with the Asian oyster.

In the letter, sent to state and federal resource agencies along the East Coast, Parker called for a voluntary moratorium on the deployment of ariakensis oysters in open waters “until a full biological and ecological risk assessment is completed, evaluated and discussed.”

It suggested that a National Academy Sciences review, expected to be completed next summer, may provide the needed analysis. Until then, it urged agencies to “review programmatic authorities and exercise appropriate responsibility as it pertains to this important issue.”

The letter warned that the introduction of a reproductive stock of nonnative oysters would be an “irreversible action that not only affects the states in the Bay region, but could also pose a threat to native oyster stocks along the entire Atlantic Coast where many sustainable native oyster populations and fisheries exist.”

The letter warns that the ariakensis oyster could pose a threat to the Bay’s native species, Crassostrea virginica. It could also detract from the 10-year, $100 million effort aimed at achieving a tenfold increase in native oyster populations in the Chesapeake, Parker wrote.

Meanwhile, the Virginia General Assembly approved a resolution calling for continued work with ariakensis oysters as part of a program to revitalize the state’s battered oyster industry.

The nonbinding resolution called for a continuation of efforts using sterile ariakensis oysters to establish a commercial aquaculture industry. It also supported continued research to assess any ecological risks that ariakensis oysters may pose to the Bay.

If that research fails to prove within three years that the nonnative oyster would be harmful to the Bay ecosystem, the resolution suggests that reproductive populations of the oyster be stocked in the Chesapeake.

At the same time, the resolution renewed the state’s commitment to working toward the Chesapeake 2000 agreement goal of achieving a tenfold increase of native oysters in the Bay by 2010, and encourages continued state and federal efforts to reach that goal.

Also, the Maryland General Assembly directed the state Department of Natural Resources to establish safeguards that would allow research with ariakensis oysters to take place within its portion of the Bay. Maryland officials in the past have opposed any work that would place foreign oysters in open water.

The legislation also called for an analysis of ecological benefits and risks associated with the introduction of both sterile and reproductively capable nonnative oysters into the Bay.