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Growing Higher-Value Oysters in Carolina Waters

Oct 25, 2013

South Carolina’s oysters are rich in flavor, tasting of the sea, and many are harvested from the wild in clusters and served up at oyster roasts.

But new opportunities could be expanded for farm-raised single oysters in the premium half-shell market. Farming oysters using off-bottom methods—growing them in mesh containers raised off the seabed—can produce larger numbers of the high-value “single” oyster sought by local chefs.

South Carolina growers could grow a nicely shaped, consistent product with off-bottom methods, which would allow them to break into more lucrative niche markets, says Julie Davis, living marine resources specialist with the S.C. Sea Grant Extension Program. 

“Oysters are widespread and abundant over the South Carolina coast,” Davis says. “But as far as optimal sites for growing premium oysters using off-bottom methods, we’re at the beginning. This could be an entrepreneurial opportunity for people living on the coast, including those already involved in the shellfish industry.”

South Carolina has many naturally rich, healthy habitats for oysters. Oyster farmers acquire a permit to use some bottom areas and harvest oysters from the seabed, primarily as clusters. Later, oyster farmers spread shell in those areas, ensuring that the next generations of bivalves will have a hard surface upon which to grow.

Other areas are permitted especially for mariculture, which employs various techniques to cultivate seafood products in saltwater. Off-bottom oyster farming is mariculture and typically uses single-set oysters produced in a hatchery as seed.

Hatchery-raised seed helps give the oyster a beautiful shape at the beginning. The oyster will maintain that shape, including the coveted deep cup, until harvest, as long as its growing conditions are not too crowded.

High-end restaurants serving oysters raw on the half-shell are looking for consistent supplies of nicely shaped oysters.

“People eat with their eyes,” says Davis. “If you’re paying a premium for an oyster in a restaurant, you’re interested in food presentation and the dining experience. You’re looking for pretty oysters.”

The abundance of oyster spat in South Carolina’s coastal waters results in oyster clusters and few naturally occurring single oysters. Oyster larvae, barnacles, and algae attach to older shells on existing reefs creating the clusters of oysters that we enjoy. But that also causes crowding on the reef, which creates long, skinny oysters.

For individual oysters to achieve a more desirable shape (wider shell, deeper cup), they require space. So researchers and oyster farmers have devised various methods to allow them to do just that.

For example, oyster farmers in some regions of the country raise oyster seed in cages that are periodically raised out of the water to air dry. Large seed can withstand the air-drying by clamping shut. But when younger, newly settled fouling animals such as barnacles are deprived of water, those animals die.

“They might be out of the water for 18-to-20 hours,” says Davis. “This reduces fouling on the cage and on the oysters. Reduced fouling gives the seed more space to grow when the cage is dropped into the water again.” Preventing growth of other animals on the oysters is key to growing a nicely shaped oyster and keeping labor costs low.

Today, oyster farmers in many regions around the world are using various off-bottom methods to reduce fouling and grow steady supplies of premium oysters for the lucrative high-end restaurant market.

“We need to find the most suitable methods and locations to grow South Carolina oysters for the half-shell market,” says Davis. “There are many different types of gear available, so we don’t need to reinvent the wheel. Let’s test the gear that others have used successfully.”

Oyster farmers need detailed information about new oyster-farming methods before investing in expensive seed and gear. So Davis and her colleagues aim to identify optimal sites to grow out oyster seed along the South Carolina coast. Then they will install off-bottom technologies with oyster seed of various ages to study their survival and growth rate. This will help determine future costs of production for oyster farmers.