Monday, June 1, 2009

Virginia Oyster Aquaculture: Sea Grant Article

Spat-on shell and the future of Virginia oyster aquaculture
By Phil Marsosudiro with additional reporting by Margaret Pizer
Virginia Marine Resource BulletinSpring 2009, Vol. 41, No. 1

It looks like a dirty baseball sitting under wet paper towels in a cooler, but it’s actually a bundle of live oyster larvae, some 20 million of them, purchased for $4,000. Michael Congrove—Remote Setting Extension Agent for the Virginia Seafood Council—lifts them out of the cooler and puts them gently into a bucket of clean seawater. He gives them a stir and waits, then pulls a few out and places them under his microscope to check their bellies (dark means they’re well-fed) and to make sure their gills are clear. If the larvae are healthy and they’re treated well for the next eighteen months, there’s a decent chance that they’ll turn into 600 bushels of oysters. Sell them at $25 a bushel, and that’s a $15,000 home run off a $4,000 baseball.
This is the dream of spat-on-shell oyster cultivation.
As aquaculture techniques go, spat-on-shell is not very complicated. You take a 10-foot diameter tank of water, drop in bags of old oyster shells, add a large batch of larvae, and wait a few days. If you’ve done it right, ten or so larvae will have settled and metamorphosed into tiny juvenile oysters (called spat) on each of the old shells, just like they would do in the wild. Then you take the bags of spat-on-shell and place them on leased bottoms in the open water. If all goes well, in about a year-and-a-half you’ll be harvesting full-grown oysters, ready for shucking.
“It’s almost like following a recipe,” says James Wesson, PhD, of the Virginia Marine Resources Commission (VMRC). But he adds that if you want to make a living from it, you need three things: First, you need the proper ingredients; second, you need to work with care and skill; and third, you need an environment that will support your efforts.
The Proper Ingredients Virginia’s first experiments with spat-on-shell date back to the 1980s. But at the time, the pieces weren’t all there to make it work. “Disease was widespread, and we didn’t yet have a broodstock of disease-resistant oysters” that could grow to market size in sufficient quantities to justify the spat-on-shell effort, says Wesson. So Virginia had to put the idea aside while they worked on improving the broodstock.
“First, we’ve developed a disease-resistant oyster,” says Wesson. It isn’t immune to disease, but it can stay healthy long enough to get to market size, and that’s all that is needed. “Second, we’ve learned how to breed triploid oysters—sterile oysters that put all their energy into a fast growout, and none into breeding.” These improvements have put spat-on-shell back on the table and locked in the first key ingredients for a Virginia oyster revival.
“Right now, most of the shucked oysters that we ‘produce’ in Virginia are shipped in from the Gulf of Mexico and elsewhere,” says Wesson. They’re a more expensive and less reliable source. For flavor, for predictability, and for profit, “we want to produce oysters that are grown in Virginia, not just shucked in Virginia.”

Mastering the Technique
After Virginia developed better broodstock and a suitable technique for cultivation, the next step was to put spat-on-shell into practice. In 2005, a dozen oyster producers began working with VIMS, VMRC, and other partners to see how spat-on-shell would work for them. After three years of progress, they decided to cross the threshold from pilot projects into independent commercial production.
To help the producers make this transition happen, Virginia’s Fishery Resource Grant Program provided funds for Congrove to work with them intensively for one year. In 2008, Congrove helped each company run several sets of spat-on-shell production—from tank preparation to larvae-setting to planting the spat-on-shell in Virginia waters. With each set, commercial staff acquired more skill and sophistication with the technique, until the end of the year when all of the participating firms were ready to conduct spat-on-shell cultivation without help from Commonwealth staff.
“The collaboration really got us off the ground,” says A.J. Erskine of the Bevans Oyster Company. While he and his peers might have started spat-on-shell by themselves, Erskine says, “Our progress would have been much slower and would have cost much more. Because Virginia backed us up with technical and financial support, the opportunity was a lot more tangible.”
Rufus Ruark Jr. of the Shores and Ruark Seafood Company echoes Erskine’s comment: “We already knew about the technique because it had a long history elsewhere.” But for his own company? “Seeing is believing, and seeing how it did work (not just how it might work) was what everybody learned. I’ve learned a lot about the larval end of it. At first it felt like, ‘just put the larvae in with the shell? That’s not gonna do anything,’ But then we pull our shells up several days later, and lo and behold there’s fifteen oyster on it.”
“Once I see that I can make money off it, I’ll go off on it,” says Ruark. “But the Commonwealth setting us up with the program is a big help—a real deciding factor. And the continuing help that they give us is a big thing.”

Supportive Environment
The final piece of the puzzle for Virginia oyster growers has been a supportive economic and regulatory environment that has helped encourage both small- and large-scale aquaculture efforts.
Although spat-on-shell aquaculture for shucked oysters is new, Virginia has more than a decade of experience in aquaculture for individual oysters that are sold on the half-shell market. Aquaculture for individual oysters is a much more labor-intensive and expensive process than spat-on-shell aquaculture. But the resulting product (which is sold in the shell, unshucked) can be sold for a much higher price.
Annual sales of Virginia-grown aquacultured oysters (half-shell and shucked) increased six-fold over the three-year period from 2005 to 2007. Several large commercial growers got in on the action—either adding aquaculture to shucking houses or starting new commercial aquaculture enterprises. Oyster hatcheries have also opened in several parts of the state, and the expanding Eastern Shore oyster aquaculture landscape now includes a major hatchery.
Oyster growers like Doug McMinn, who founded his Chesapeake Bay Oyster Company in 2003, say the motor behind the success of Virginia oyster aquaculture has been steady growth in the market for Chesapeake Bay oysters, the availability of local shucking houses, and the support of state institutions like VIMS that have helped develop the science to set oyster growers on the right track.
“I think part of why the [aquacultured] clams have done so well and why oyster farming now is doing well is because the state was in at the beginning to help come up with some of the technology but then the guys had to start putting down their own money and putting themselves on the line,” says McMinn. “They’re not going to walk away from the buck that they put down without a fight.”
McMinn thinks Virginia has reached the right public-private balance to foster growth in the oyster industry. “This state has a lot of private individuals who run hatcheries and do a really good job, and they’re willing to increase volume as the demand dictates.”
In addition to hatcheries, shucking houses are an important component of the supportive environment in Virginia. In other East Coast states, many shucking houses went out of business as natural oyster harvests declined in the second half of the twentieth century, but in Virginia, the shucking houses began trucking in oysters from the Gulf Coast and were able to stay afloat.
Now, as aquacultured oysters are on the rise, these shucking houses are a natural place for those oysters to go. “Because we have shucking houses around here, we automatically have another market” for individually grown oysters that might not be suitable for the half-shell market because of their size or quality, says McMinn. Those shucking houses are also a natural market for spat-on-shell oysters from Virginia, and many of them are getting into the spat-on-shell oyster cultivation business themselves.

The Forecast
For all the progress they’ve made thus far, Virginia scientists and oyster producers are far from knowing that spat-on-shell will be a guaranteed success. Disease, pollution, weather-driven changes in salinity, and predation from the cownose ray remain as known risks or wildcards that could derail the potential of spat-on-shell production in Virginia.
Despite the uncertainties, commercial producers remain hopeful. “
We’ve already been working with some of the guys on better systems” for spat-on-shell, says McMinn. “The more we do to farm raise, whether it’s spat-on-shell, whether its cage, whatever you’re doing, it takes pressure off the wild stocks. I think spat-on-shell is going to be a great thing for restoration.”
At Kellum Seafood, Vice President Tommy Kellum says, “at this point, spat-on-shell is producing maybe 10,000 bushels a year for us. It’s certainly in a juvenile stage for us. But given the size of our leased acreage, we could get to a point where fifty to sixty percent of our oyster supply would come from spat-on-shell in five to eight years. With spat-on-shell, I can actually see us generating enough oysters to keep the plant running year round, with 100 people working.”
Rufus Ruark Jr. sums it up. “I think this is something everyone’s gonna be happy with.”

Crediting Oysters for Helping Clean the Bay
The Commonwealth has a strong record of supporting the science and training needed to help oyster growers succeed. In the coming years, Virginia may also have the opportunity to provide incentives for both amateur oyster gardeners and commercial aquaculture operations based on the benefits oysters provide to the environment by filtering and cleaning Chesapeake Bay waters.
One simple incentive would be a tax credit for Virginia residents who grow oysters off of backyard docks or floats. In the 2009 session of the Virginia General Assembly, a bill to establish such a credit was put forward by Senator Ralph S. Northam who represents District Six, including Accomack, Northampton, and Mathews Counties and parts of Virginia Beach and Norfolk.
“If people get involved by putting an oyster float out, the next thing you know they might realize maybe they don’t need as much fertilizer on their lawn,” says Northam, arguing that an awareness of the nitrogen, phosphorous, and other pollutants that oysters help remove from the water would have cascading effects on the behavior of coastal residents. Although the bill had to be withdrawn due to this year’s budget crisis, Northam plans to reintroduce it in the future.
A second incentive would encourage large-scale oyster aquaculture by providing “nutrient credits” to oyster growers based directly on the pounds of nutrients removed from Bay waters.
One way to create monetary value for a credit is through nutrient trading. Nutrient trading is already on the books in Virginia. Passed by the state legislature in 2005 and slated to become mandatory in 2011, the system limits nitrogen and phosphorous output from point sources like wastewater treatment plants. Plants that exceed the limit can buy credits from others whose output is below it.
Point sources can also balance their emissions by buying nutrient offsets from point or non-point sources. The Department of Environmental Quality has approved several types of agricultural offsets. For example, farmers can generate offsets by reducing the use of nitrogen fertilizer or by leaving some of their land untilled.
A team of researchers, including Kurt Stephenson of Virginia Tech, Alex Miller at the Gulf States Marine Fisheries Commission and Bonnie Brown and Colleen Higgins at VCU are researching ways that oyster growers could generate nutrient credits. Oysters remove nutrients from the water by filter feeding. When the oysters are harvested, the nutrients they’ve eaten and incorporated into their tissues are permanently removed from the water. Oysters also accelerate denitrification, which transforms nitrogen into a gas that is biologically unavailable.
Stephenson and Miller say that one major obstacle to incorporating oyster aquaculture into the nutrient trading system is the complicated science required to quantify how much nitrogen oysters remove—which can depend on the size of the oysters, where they are grown, and a variety of other factors. If these issues can be overcome, nutrient credits promise yet another source of support for commercial oyster aquaculture operations. Oyster growers like Jack White, owner of New Point Oyster Company, hope that Virginia will be able to include oysters in its nutrient trading system. “The time is ripe to recognize the role shellfish can play in cleaning up the Bay” and to make that recognition pay for oyster growers, says White.

A Practical Manual
A group of Virginia scientists and seafood companies collaborated to produce “A Practical Manual for Remote Setting in Virginia,” a booklet that outlines a step-by-step process for obtaining oyster larvae, getting them to set on shells, and growing them out to harvestable sizes.
The manual was written by Michael S. Congrove of W.E. Kellum Inc. and the Virginia Seafood Council, Dr. James A. Wesson of the Virginia Marine Resources Commission, and Dr. Standish K. Allen Jr. of VIMS with collaboration from ten Virginia seafood companies and funding from the Virginia Fishery Resource Grant Program, which is administered by the VIMS Advisory Services department.
The ten seafood companies that participated in the project are Bevans Oyster Company, Cowart Seafood Corporation, J&W Seafood, Kellum Seafood, Mobjack Bay Seafood, Purcell’s Seafood, Sea Farms, Shore Seafood, Shores and Ruark Seafood, and Terry Brothers.
The manual is available for free online or for $10 in print. Go to or email

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Sowing The Seeds