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  • Oyster Gardening

RI-OGREStarted with 18 volunteers in 2006, this project enlists waterfront property owners to maintain an oyster nursery at their docks. Called the Oyster Gardening for Restoration and Enhancement (ORGE) Program, this effort grew to 58 participants in 2007 and 73 in 2008 when we were able to distribute an estimated 750,000 young oysters to restoration sites in Narragansett Bay, Rhode Island's coastal ponds and Block Island. To date, almost 3 million oysters have been planted for restoration; our goal for 2013 is 100 oyster gardeners producing 1,000,000 oysters.

Oyster seed for this project is produced by our students and staff in the shellfish hatchery using a technique known as "remote set" in which larvae are set onto bags of clam and/or oyster shell. These bags are then distributed to the volunteer gardeners who maintain them over the summer. In this way, each oyster gardener helps us grow between 10,000-12,000 young oysters which we recover in the fall and plant onto restoration oyster reefs. 

Why do this silly thing?

Ecosystem Services: Oysters (and shellfish in general) play an important role in maintaining environmental conditions that promote the productivity of local waters. Some of the services oysters contribute to an ecosystem include:

  • Improving water clarity by filtering up to 50 gallons of water per day per oyster with a particle retention size of 2-3 microns.
  • Removing nitrogen and other nutrients from coastal waters directly and indirectly through the consumption and transition of phytoplankton from floating particulates to either oyster tissue or to the sediment.
  • Increasing the rate of nitrogen removal from the coastal ecosystem by promoting anaerobic denitrification below the oyster bed.
  • Increasing the complexity of the bottom providing increased habitat value to fish and other important marine organisms.
  • Contributing to the value of our coastal marine economy by providing job opportunities and tax revenue through commercial and recreational harvesting.

The oyster is an important component of our coastal waters, but for the past few decades their numbers have diminished greatly along the eastern seaboard. Given their unique biology and requirements for reproduction and recruitment, most coastal states have programs intended to repopulate this species.

Here in New England, the bottlenecks to oyster restoration are few but significant:

  1. Disease: Two prominent diseases (dermo and MSX) are the primary agents responsible for the wide-spread decline of oyster populations. Researchers have demonstrated that selectively breeding oysters that have survived intense disease pressure in the wild can impart a degree of resistance to their offspring. Using this knowledge, we have initiated an oyster breeding program at our hatchery where native oysters from local areas with high disease pressure are crossed with southern disease resistant lines to impart increased disease resistance. These are the seed deployed for restoration.
  2. Bottom Habitat: Oysters preferentially set (the transition from swimming larva to bottom-dwelling organism) on oyster or clam shell, collectively referred to as cultch. Therefore, restoring oysters to an area requires the restoration of a bottom populated with large amounts of cultch. During recent years, environmental management agencies have frowned on cultch programs, treating shell as industrial waste or dredge fill. Through re-education, we have impressed on local regulators that shell is important to oyster habitat and have gained permission to clutch selected areas in the bays. In this manner, we effectively build new, protected oyster reefs to serve as spawning sanctuaries for the recruitment of new oyster larvae to our coastal water.
  3. Labor: The third bottleneck is the labor required to rear young oysters (spat) to a size of 1 to 1.5 inches, where they are much less susceptible to crab and snail predation. Once out of the protection of the shellfish hatchery, we use conventional commercial aquaculture technology (bag and raft system) to house and protect the spat through the first summer of growth. This is technically simple, but requires vigilance and maintenance to ensure the oyster cages are secure and free of biofouling that obstructs water flow.

OystersWe created the OGRE Program to solve this last bottleneck, and recruit volunteer coastal landowners to assist us in rearing the juvenile oysters. Oyster Gardening is a strategy that has proven highly successful in the Chesapeake Bay (MD & VA), Mobile Bay (AL) and in North Carolina. By employing volunteers, we receive the labor assistance we need, but also carry out a not-so “hidden agenda” that involves educating the public about the marine ecosystem, and providing an opportunity for coastal landowners to participate in ecosystem restoration.

Each fall, the young oysters are recovered from the OGRE volunteers and transplanted to permanent restoration sites where they are allowed to grow undisturbed. As these oysters grow and reproduce, they provide a source of (putatively disease resistant) larvae for the replenishment of the native oyster in Rhode Island waters.