The Virginia Seafood Council is drafting a five-year plan that will likely call for using millions of fast-growing, nonnative oysters in aquaculture in the Chesapeake Bay, something that could revitalize the state’s beleaguered oyster industry.
But a flurry of papers from government agencies, scientists and others are calling for a go-slow approach when the industry groups’ plan is submitted for action by the Virginia Marine Resources Commission, probably this spring.
The position statements generally oppose any large-scale aquaculture, even with sterile oysters, until more safeguards are in place to help ensure that oysters are not accidentally released into the wild.
In addition, the papers call for more extensive research about what impacts — both positive and negative — the nonnative oysters could have if a reproducing population becomes established in the Chesapeake.
The spate of papers was prompted by rapidly growing interest in the use of Crassostrea ariakensis in the Bay. Recent studies have found that the species, a native of Southeast Asia, grows much faster than the native oyster, Crassostrea virginica, and appears immune to the diseases that have devastated the native oyster population.
To date, field tests have been on a small scale, using sterile ariakensis oysters reared by the Virginia Institute of Marine Science. In 2000, about 6,000 ariakensis oysters were placed in the Bay, and 60,000 were used in 2001. They not only grew fast with high rates of survival, but market tests have indicated a potential high demand for the product.
As a result, watermen in both Virginia and Maryland are interested in dramatically escalating the use of sterile oysters in aquaculture. And, many advocate an outright release of reproducing oysters into the Chesapeake — a position also supported by many county governments in Virginia, where the once-thriving oyster industry has been nearly wiped out.
But VIMS, which has conducted almost all of the work with ariakensis, said in a position statement that any intentional introduction of reproducing oysters would be “imprudent” at this time.
“The ecological consequences of introducing this oyster to the Chesapeake Bay are too uncertain to support such an introduction,” VIMS said. “From discussions to date, it is clear that the broader marine science community shares this view.”
VIMS also cautioned against a large-scale increase in ariakensis aquaculture — even with sterile oysters — until regulatory and “biosecurity” safeguards are in place to help prevent an accidental release into the Bay. VIMS’ hatchery is where ariakensis oysters are produced.
To create sterile oysters, VIMS breeds female oysters with two sets of chromosomes with males that have four sets of chromosomes, creating offspring with three sets — known as triploids — that cannot reproduce.
Over time, though, research has shown that a small percentage of the triploid oysters begin to revert to diploids, with two sets of chromosomes. If a male and female reverted in close proximity, they may be able to reproduce, although lab work has not yet shown that such “reverted” oysters can produce offspring.
Because of the likelihood of reversion, there is concern that large-scale aquaculture efforts would eventually lead to an accidental introduction of reproductive-capable oysters in the Chesapeake.
That concern has generated opposition by some to any significant increase in aquaculture with the oyster.
A statement from the Bay Program’s Federal Agencies Committee — which represents the EPA, Army Corps of Engineers, National Oceanic and Atmospheric Administration, Fish and Wildlife Service and others — said aquaculture with ariakensis “should not be initiated until significant unanswered questions … are addressed through scientific research.”
¹ separate white paper drafted by the U.S. Fish and Wildlife Service’s Chesapeake Bay Field Office, while acknowledging that the oyster may hold large potential economic and ecological benefits to the Bay, also cited a lack of basic information about the oyster. “More biological and ecological information will be needed to determine if the benefits do outweigh the risks.”
The Chesapeake Bay Foundation agreed that a decision about large-scale aquaculture “cannot be made responsibly” because of a lack of information about the ecological risks and benefits.
Many of the statements noted that ariakensis is poorly studied, even in its native habitat. It’s unknown, for example, whether it builds reefs — an important habitat for other species — like the native Bay oyster.
It’s also unknown whether the feeding habits of ariakensis differ significantly from the native oyster, which could affect the Bay’s food web, or the degree to which it would co-exist — or compete — with the native oyster or other Chesapeake species.
In its position paper, the CBF called for an independent outside review by the National Academy of Sciences to outline needed research about ariakensis, which could, in turn, be used to help weigh its potential risks and benefits.
Noting concerns that someone impatiently waiting for those research results might try to obtain ariakensis oysters on their own and place them in the Bay, the CBF called for an educational campaign to make people aware of potential dangers.
Such imported oysters, if not inspected in a laboratory, could harbor diseases that would also be introduced into the Bay. It is believed that the oyster disease MSX was introduced to the Chesapeake in the 1950s as the result of a failed attempt to introduce the Pacific oyster, Crassostrea gigas, to the region. Since then, MSX and another disease, Dermo, have devastated the native population.
The federal agencies statement and the Fish and Wildlife Service paper both questioned whether any large-scale work could proceed without federal approval. They noted that the Army Corps of Engineers usually must approve the placement of structures — such as those needed by large-scale aquaculture — in waterways.
In addition, the the Fish and Wildlife Service said, the use of the foreign oyster may require review under the National Invasive Species Act of 1996 if there is a danger that it could become an “aquatic nuisance species.”
Others, though, have expressed doubt that the federal government has legal jurisdiction over the use of ariakensis.
The federal agencies’ paper also expressed concern that interest in ariakensis could detract from efforts to restore the native oyster. The Chesapeake 2000 agreement calls for achieving a tenfold increase in the population of native oysters by 2010, something that is expected to cost about $100 million, half of which would come from the federal government.
The CBF echoed that concern, saying that the large-scale restoration of virginica has only just begun, with substantial public and private resources only recently committed to an effort expected to take at least 10 years. “Based on the results of the early stages of this long-term effort, there is considerable optimism that the native oyster can be restored to Chesapeake Bay, providing both economic and ecological benefits,” it said.
Although wary of large-scale aquaculture at this time, both VIMS and the CBF specifically supported continued market tests of the foreign oysters, similar to those conducted in the past two years.
“Carefully designed and monitored commercial trials serve the dual purpose of providing data on the long-term aquaculture potential and the ecological impacts of this species,” the VIMS statement said.
But some statements left the door open for wider use of ariakensis in the future — perhaps even an introduction of a reproducing population — if efforts to recover the native species falter.
The CBF said it was possible that ariakensis “could at some point in the future be considered as a tool for reinvigorating the oyster industry and potentially for restoring certain ecosystem functions.” But it said more information was needed before such a decision could be made.
Similarly, the Fish and Wildlife Service paper said “it is conceivable that the potential economic and ecological benefits of introducing the Suminoe oyster [ariakensis] to the Chesapeake Bay could outweigh the risks to native oyster stocks.
“Such an introduction could possibly revitalize a dying oyster fishery, increase water clarity, reduce fishing pressure on the native oysters, and generate hard substrate for native oyster attachment and growth.”
But, it said, “more biological and ecological information will be needed to determine if the benefits do outweigh the risks.”
Several position statements said that any decision about introducing the oyster should not be made by Virginia alone, because it could affect other states along the coast. VIMS, for instance, called any introduction of reproducing oysters “a management decision of far-reaching consequences” and said it should involve stakeholders from other states.