Fish and Aquatic Conservation

 

Oyster Feasts and Reefs
Shell recycling builds fish habitat, protects property

 

Student-designed and student-built, this bridge at the Rio Grande Silvery Minnow Sanctuary near Albuquerque, New Mexico, is the product of a cooperative effort to engage, educate, and employ youth in conservation projects.
In South Carolina, oyster reefs thrive in the intertidal zone providing habitat, wave breaks, sediment traps, and cleaner water. Credit: Roman Crumpton/USFWS

 

On almost any cool fall night in coastal South Carolina, a unique scent permeates the air, as if someone has filled a hot tub with sea water and set it on high. The scent causes some to respond like a bloodhound on the hunt. It is oyster season again.

Oyster feasts have been popular social events in coastal South Carolina since the first people populated the Atlantic shores. Native American settlements have been located by the shell rings left behind. These rings date to 4,500 years old, and the significance of the shell rings is thought to be ceremonial. Archaeological evidence of early Europeans harvesting oysters is also apparent. Shell is often found in dumps, or middens, along with other items including glass and ceramics. Beyond ceremonial use, oyster shell was also used in projects such as dike building, as well as a binding element of mortar, the evidence of which can readily be seen in the foundations of many historical buildings in coastal South Carolina. But perhaps most significantly, spent oyster shell was rarely returned back to the water from whence it came.

A stack of bagged shells sits at a public drop off site at Bears Bluff National Fish Hatchery. The kiosk informs the public about the importance of conservation.


A stack of bagged shells sits at a public drop off site at Bears Bluff National Fish Hatchery. The kiosk informs the public about the importance of conservation.
Credit: Roman Crumpton/USFWS

Boy Scouts volunteer frequently to bag shells for future oyster reef projects.
  Boy Scouts volunteer frequently to bag shells for future oyster reef projects. Credit: Roman Crumpton/USFWS

The eastern oyster is found on both the Atlantic and Gulf coasts of North America. In South Carolina, mature oysters spawn in water temperatures that exceed 68 degrees. A free-swimming larval oyster is formed and progresses through several life stages which only takes a few weeks. This part is essential: the larval oyster seeks out other oyster shell and attaches as a "spat," or the juvenile form of a sessile oyster. As a result, oysters build upon themselves into oyster reefs, and as the years pass they become extremely complex in their architecture. These reefs are beneficial in many aspects: they provide essential habitat for a variety of aquatic organisms beyond themselves, and since oysters filter water to find their food, they clean the sea through the filtering process. Moreover, the oyster reefs reduce shoreline erosion by dissipating storm and wave energy. Less shoreline sediment in the water means better fisheries.

Over the years, a substantial commercial and recreational fishery existed for the eastern oyster. Until recently there has been no concerted effort to return shell to the water. Bears Bluff National Fish Hatchery on South Carolina's Wadmalaw Island partnered with the South Carolina Oyster Restoration Enhancement (SCORE) program to do just that—get shell back where it's needed—in the tidewaters. The SCORE program has operated since 2001 as an entity of the South Carolina Department of Natural Resources.

Acquiring oyster shell continues to be the challenge. Bears Bluff National Fish Hatchery has established an oyster shell drop-off site where the public can bring their shells following a roast. The site employs an informational kiosk used to educate the public about the oyster restoration program, and why shell is needed. The SCORE program has drop-off sites at many state-maintained boat ramps throughout coastal South Carolina. Partnering with local caterers and restaurants has proven to be a reliable source of shell. Oyster shell can be purchased as well; however, the costs can be limiting.

 

A freshly built oyster reef will soon flourish into a rich fish habitat and wave break. Credit: Roman Crumpton/USFWS
A freshly built oyster reef will soon flourish into a rich fish habitat and wave break.

After the shell is collected, it cannot be returned to the estuary for at least six months. This is called the "curing" time. Curing the shell is necessary to protect local oyster beds from diseases that may have infected oysters from other areas of the country or even other local estuaries. Disease is a major threat to existing reefs. Cured shell is then bagged in mesh sacks and stacked, waiting then to be arrayed in the water. Bagging is often done by volunteers from naturalist groups, youth summer camps, and school groups.

In 2012, Bears Bluff National Fish Hatchery and the Charleston Ecological Service's Coastal Program started building oyster reefs for landowners who are experiencing erosion near their waterfront homes. The process requires an initial site visit at low tide to determine feasibility and an approach to reef-building. Factors include: ability to increase fish habitat, sea bottom type, exposure to erosion, and accessibility. A plan is devised and permission is then sought through the South Carolina Department of Health and Environmental Control. Upon acknowledgement of compliance to South Carolina's coastal zone management program, reef building commences in the intertidal zone.

Four years later, a rebuilt oyster reef is robust and well established.
Credit: Roman Crumpton/USFWS
Four years later, a rebuilt oyster reef is robust and well established.

Here's how it's done in the water. Bagged shells rest on top of wooden pallets. The pallets are dropped on the sea floor. Steel rebar stakes driven through the reef and pallets secure it in place. Biologists with the Bears Bluff National Fish Hatchery and the Coastal Program make follow-up visits to check on the condition of the reefs as well as monitor sediment deposit behind the reefs—a byproduct of wave energy dissipation by the new reef. In these areas behind the reefs there is a significant increase in marsh plants, mainly smooth cord grass, which is nursery habitat for fish.

Oyster reefs enhance fish habitat, clean the water, reduce erosion, and restore marsh habitat. Increasing marsh habitat buffers the effects of energy storms and waves carry. The new marshes trap pollutants and provide essential habitat for other species of aquatic organisms including crabs, birds, fish, and you guessed it—oysters. And that's all good for people, too.

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Roman Crumpton is a fish biologist at Bears Bluff
National Fish Hatchery on Wadmalaw Island, South Carolina.


Last updated: January 13, 2014