Plans to place 1 million sterile foreign oysters into the Bay and nearby waters won approval from the Virginia Marine Resources Commission in February, despite the misgivings of two panels of scientists who reviewed the issue.

By a 5-1 vote, the commission approved a request by the Virginia Seafood Council to allow a large-scale experiment to see if the fast-growing, disease resistant oysters can be profitably grown in aquaculture, processed and sold.

Two previous tests have been done with the oysters, Crassostrea ariakensis, but at much smaller scales: The largest only used 60,000 oysters. But the results showed the native of Southeast Asia could survive the diseases that kill native oysters, and they won favorable reviews in taste tests.

The findings have excited many watermen in both Virginia and Maryland as the population — and harvests — of the native C. virginica have hit all-time lows because of intense disease pressure in recent years.

“The Virginia oyster industry is in dire straits,” council spokeswoman Frances Porter told the commission.
The council made significant alterations from a similar proposal last year, which it subsequently withdrew amid criticism. The changes, which include using a more reliable technique to render the oysters sterile, helped the new proposal win support from both the Virginia Institute of Marine Science and the Chesapeake Bay Foundation.

The sterile oysters would be produced by mating oysters chemically treated to have four sets of chromosomes with natural oysters with the normal two sets. The result are “triploid” oysters with three sets of chromosomes, which cannot reproduce.

Last year, the council had proposed using oysters chemically treated to have three sets of chromosomes, a less reliable technique which could have resulted in 10,000 oysters — out of the 1 million in the project — being capable of reproduction.

Nonetheless, the new proposal was still criticized by a special panel convened by the Bay Program to review the proposal, and by the co-chairs of a National Academy of Sciences committee that was formed to study the pros and cons of using the nonnative species in the Chesapeake.

“At present, there is insufficient scientific information available to thoroughly quantify and evaluate the risks and benefits of introducing this species into Virginia waters,” the co-chairs of the NAS panel wrote in a letter to the VMRC. “Even less information is available for assessing the potential spread of C. ariakensis in the Chesapeake Bay and into the coastal waters of states along the Atlantic seaboard,” they added.

The NAS panel, convened last year at the request of the Bay Program and state and federal agencies, is examining the economic and ecological implications of using sterile C. ariakensis oysters in aquaculture, as well as of the outright introduction of a breeding population into the Bay. Their report is expected this summer.

Meanwhile, a separate panel of scientists and state and federal officials convened by the Bay Program to review the seafood council’s proposal also expressed misgivings, warning that statistically, about 1,000 of the oysters used in the project may be capable of reproducing. Also, they said studies show that triploid oysters, over time, can begin to revert to normal oysters with two sets of chromosomes and could become capable of reproducing. That could risk introducing a breeding population into the Bay.

The panel also said questions about whether the oysters may accidentally introduce a disease or virus that may affect native Bay life had not been fully resolved. Panel chair Frederick Kern, a National Oceanic and Atmospheric Administration scientist, wrote the VMRC that after extensive discussion, “the panel rejects this proposal as written.”

In approving the measure, the VMRC did adopt some added precautions recommended by the scientists.
During the experiment, oysters will be monitored for any signs of chromosome reversions. Also, the commission set an end date for the experiment of April 2005, at which point any remaining oysters would be removed from the water to minimize the risk of reversion, which increases over time.

The Bay Program panel, though, had recommended a June 1, 2004 end date for the experiment.

The oysters that will be used in the experiment are being reared at VIMS, and are expected to be ready to be distributed to about a dozen different growers by late spring or early summer.

In its proposal, the seafood council said it envisioned a “brand new” industry in which millions of hatchery-reared, sterile C. ariakensis oysters will be reared in aquaculture, instead of harvesting native oysters on the bottom of the Bay, as in the past. It believes 200 million to 300 million of the oysters could be reared annually in aquaculture.

The council stated there is “little or no financial return on planting native oysters in Virginia” because most die of disease before reaching market size, but C. ariakensis “thrives” in the Bay, at least in aquaculture.

Virginia’s oyster industry has been particularly hard hit because the state’s high salinity water is more conducive to oyster diseases. Harvests of the native oyster have fallen from about 4 million bushels per year in the 1950s to 20,000 bushels in recent years in the state.