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#07-237 August 27, 2007

Oyster reefs enhanced with alternative materials

An oyster reef restoration project comparing alternative materials to different types of commonly used natural shell recently concluded planting efforts at two sites in Awendaw, near Bull’s Bay and the Intracoastal Waterway. 

Biologists and fisheries managers with the S.C. Department of Natural Resources (DNR) are looking at ways to enhance and restore oyster resources and their related ecological role as critical habitats and significant biological filters.  As shells become increasingly difficult to obtain, states that manage oyster resources are in greater competition with one another for the limited shells. This project is comparing the use of several alternative materials at once that have necessary properties, such as a hard surface for young oysters to attach, in areas where the addition of shells would normally be employed.  The project, funded by the Saltwater Recreational Fishing License Program, was initiated as a proactive response to increasing costs and the decline in available oyster and whelk shells, both traditionally used by DNR for oyster reef restoration and enhancement.

The closure of oyster shucking houses and canneries in the state over the past few decades, paralleled with the growing popularity of backyard oyster roasts, have contributed to greater demand for material suitable for replenishing or enhancing the state’s shellfish habitats. The increasing need to purchase many tons of shell annually for DNR’s planting program, from vendors located in NC and other states, supports SC’s current shell recycling program. Successful recruitment and retention of one or more readily available materials may be a great benefit to DNR and efforts towards sustainable management of shellfish habitats. These new methods are a necessity with the increase of coastal development and associated impacts, and recreational shellfish gathering that have affected critical oyster habitats.

South Carolina has over 2,000 acres of oyster habitat along the shoreline, with over 90% of the resource located in Beaufort and Charleston counties. The habitat created by oyster reefs enhances the area for a variety of other marine species, such as crabs, shrimp and small fish. Larger fish and crustaceans frequent oyster reefs to prey on the species living there. Oysters are also significant water column filterers, potentially controlling algal blooms and improving water clarity. Furthermore, intertidal oyster reefs provide a natural buffer that can protect and bolster shorelines from erosion in heavily trafficked areas. Juvenile oysters require a suitable, hard shell in which to attach and grow, and DNR biologists predict that alternative cultch materials should be able to provide this critical substrate. Other states such as Florida annually use 1000’s of tons of fossil shells and other materials in lieu of oyster shells.

Loren Coen, DNR’s shellfish research manager and coordinator of this recent planting effort, worked with other DNR staff and volunteers from The Nature Conservancy to use a shell planting barge, trailers and tractors to construct 20 adjacent oyster reef footprints within the Cape Romain Wildlife Refuge. In conjunction with staff from the U.S. Fish and Wildlife Service, the group effort involved the use of recycled concrete, limestone, fossil oyster shells, and SC and Gulf oyster shells. In addition to the reef planting in Cape Romaine National Wildlife Refuge, similar deployments took place in Charleston, in the Folly River area and near the Buck Hall Landing. This comparative restoration used the same materials, with the addition of whelk and granite, as was used near the Awendaw sites. The project will be closely monitored for the next two years to determine the relative success of each material based on oyster recruitment, retention (loss or sinking), and resistance to waves and boat wake impacts.  DNR staff will also measure shoreline erosion at areas associated with the fringing salt marsh behind and between the reefs.

The project will enable researchers to continue an avenue of research that DNR has followed for over 13 years. Information gained will be used to improve existing and future shellfish restoration efforts. Additional information here and here.

DNR protects and manages South Carolina’s natural resources by making wise and balanced decisions for the benefit of the state’s natural resources and its people.

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