Seafood group seeks new tests with ariakensis
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Buoyed by test results it called an “eye-opener,” the Virginia Seafood Council hopes to place 1 million sterile Asian oysters in the Bay this summer to see if they can be harvested within a year.
The industry trade group said results from its deployment of 800,000 oysters in the fall of 2003 were a “complete success” and offered a tantalizing hint that a profitable aquaculture industry might be based on sterile foreign oysters.
The test showed that the oysters were profitable not only for the high value—though limited—half shell market, but also for use by seafood processors, which shuck larger numbers of oysters for their meat.
In the study, eight growers received 100,000 oysters apiece. Participants invested between $3,000 and $7,500 and had returns of $10,000 to $20,000, according to A.J. Erskine, project manager for the council.
“With 50,000 or 100,000 oysters, you can certainly make a couple of thousand dollars, but the potential exists for a more sizeable profit,” Erskine said.
He said the potential existed for rearing millions of sterile foreign oysters each year, providing relief for watermen who have been hard hit by the demise of the native oyster and are willing to switch to aquaculture. Those oysters would also be a boon for seafood processors who increasingly have had to import oysters from the Gulf of Mexico because of the lack of Chesapeake oysters.
The seafood council’s proposal won approval from a Bay Program review panel in March. It still needed approval from the Virginia Marine Resources Commission and the Army Corps of Engineers, although participants from both agencies served on the Bay Program review panel.
Exactly what role the fast-growing Crassostrea ariakensis will play in the Bay has been the center of debate for years. Tests conducted by the seafood council since the late 1990s have shown that the oysters grow fast and appear to resist diseases that have devastated the native C. virginica oysters. Further, marketing tests have shown C. ariakensis is well-received by consumers.
That has fueled huge interest in the foreign oyster, and the states of Maryland and Virginia have proposed an outright introduction of a breeding population in the Bay. That option has been hugely controversial, and is the subject of an environmental impact study.
Meanwhile, aquaculture using sterile oysters—which initially drew intense concern because of its potential for an accidental introduction—has become more accepted, especially as the seafood council has adopted new safeguards.
“I think the aquaculture option has become more palatable to a lot of folks who were initially turned off to any nonnative species,” said Jamie King, an oyster biologist with the National Oceanic and Atmospheric Administration’s Chesapeake Bay Office. “The Virginia Seafood Council is gaining some ground with the very responsible approach that they’ve taken.”
A report released by the National Academy of Sciences two years ago was generally supportive of the use of sterile oysters in aquaculture, especially as a way to gain more information about how the foreign species might behave in the Bay.
But the report expressed skepticism that growing sterile oysters would be profitable except for the high-value half-shell market, which would limit their use in the Bay. In the seafood council’s project, however, growers were able to make a profit, even when selling C. ariakensis to “shucking houses” that extract the meat for resale.
In part, that’s because processors have been forced to rely on oysters from the Gulf of Mexico to meet their needs, Erskine said. It cost them about $2,000 just in freight costs—plus the cost of the oysters.
Beyond that, tests from the last two years showed that C. ariakensis oysters produce far more meat than than oysters from the Gulf. A bushel of sterile C. ariakensis oysters grown in aquaculture produced almost two full gallons of meat, compared to less than one gallon for a bushel of Gulf oysters, the seafood council study found.
In addition, C. ariakensis has thinner shells than C. virginica, which make them easier to shuck. While the thin shell of C. ariakensis has raised concerns about its potential in the wild—some experiments have shown they are more vulnerable to predators, as well as infestations by native worms—it is a plus for shucking houses, Erskine said.
“It looks like C. ariakensis would be a great shucking oyster because they are very easy to get into,” he said. “Shuckers report that you can shuck almost twice as many ariakensis as you can C. virginica.”
That contributed to a change in the seafood council’s proposal. In its 2002 request for a large-scale test, the council had envisioned aquaculture as a potential steppingstone to an outright introduction of a breeding population. In contrast, its new proposal says the scientific community should focus on repopulating the Bay with a disease-tolerant strain of the native oyster, while the industry concentrates on “self-sufficient aquaculture” with sterile C. ariakensis oysters.
The new proposal envisions an aquaculture industry that “plants new seed every spring and harvests their crop the following spring.” The spring harvest is important to minimize the risk of an accidental introduction of breeding oysters.
The technique being used to produce sterile oysters is estimated to be 99.9 percent effective — but that still means that about 1 in 1,000 could be capable of reproducing. The likelihood of them reproducing during their first-year summer in the water is small, but it would increase if the oysters remained in the water second summer.
The goal of the new study is to determine whether oysters placed in the water around June 1 would grow to market size within 12 months, allowing growers to take advantage of the fast-growing, disease-resistant potential of C. ariakensis, while reducing potential reproductive risks.
The seafood council had proposed a similar project for 2003. But because of a delay in rearing sterile C. ariakensis, the oysters did not go into the water until October. That meant the oysters could not take advantage of the ideal summer growing season.
It was clear from the study that the oysters can reach market size in moderate to high salinity water within a short amount of time, Erskine said, but it was not clear that will happen in low salinity areas.
“What we really need to know is at the lower salinities, can we get 100 percent of the oysters to market size?” he said. “At the higher and moderate salinities we can probably do that.” In fact, he said, in high salinities, the oysters may be ready to harvest before Christmas.
A special ad-hoc panel of state and federal officials, convened by the Bay Program to review all proposals dealing with potential introductions of nonnative species, in March recommended that the seafood council’s proposal be approved.
But the panel emphasized the need to pull the oysters out of the water by June 1, 2006, to reduce any spawning risk. It said information gathered during the experiment should be used to better estimate the risk of reproduction in any future projects.
The ad-hoc panel also encouraged expanded side-by-side testing with sterile C. virginica oysters in aquaculture to allow for better economic comparisons between the two species. Recent efforts have shown that sterile C. virginica also performs well in aquaculture, although it does not match C. ariakensis. But because it is a native species, it does not require the strict “biosecurity” protocols used with foreign species.
Biosecurity concerns do raise costs, Erskine said. All of the oysters have to be grown in mesh bags or other containers that keep any from escaping; growers must write plans to remove oysters from the water in the event of hurricanes or other severe weather; and groups of oysters must be spaced apart to reduce the risk that eggs and sperm from any reproductive-capable oysters would mix.
But Erskine said the bigger issue limiting aquaculture with C. ariakensis—or the native C. virginica—is lack of infrastructure. For large-scale production, he said, expanded hatchery facilities are needed to breed oysters as well as more nursery facilities to grow them to sizes large enough to plant for final growout.
“Whether it is C. ariakensis, C. virginica, or any other species, I think there is an awful lot of potential in aquaculture,” Erskine said. “It takes a different mindset, and a lot of the large oyster shucking houses are not used to aquaculture. But I think the potential scale could be several millions of oysters each year.”
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