Oyster populations in the Chesapeake Bay have declined dramatically in the last century, largely due to parasitic diseases, overharvesting, declining water quality, and a loss of habitat. Less than one percent of historic oyster populations remains. Oyster restoration is important because oysters provide a number of environmental benefits, including reef habitat that is significant to the Bay ecosystem for animals like blue crabs and fish. Additionally, oysters are filter feeders that improve water quality.
The Native Oyster Restoration Master Plan is the Corps' plan for large-scale, sanctuary-based oyster restoration throughout the Chesapeake Bay and its tributaries in Maryland and Virginia. The master plan examines and evaluates the problems and opportunities related to oyster restoration, and formulates plans for implementing large-scale, Bay-wide restoration.
Project elements include: (1) creation of disease-free spat (oyster seeds or baby oysters) from state-owned hatcheries; (2) creation of new oyster habitat; (3) rehabilitation of existing non-productive oyster habitat; (4) construction of seed bars or reefs for production and collection of spat; (5) planting spat on the new and rehabilitated reefs; and (6) monitoring of project performance.
The Corps restores reef structure to re-establish oyster habitat where it previously existed. Maryland Department of Natural Resources produces the spat-on-shell (baby oysters) at the state-owned Horn Point Hatchery and provides for the planting of the spat-on-shell at restoration sites by the Oyster Recovery Partnership. The National Oceanic and Atmospheric Administration maps available restorable water bottom using sonar in conjunction with various ground‐truthing methods and also funds the production and planting of spat-on-shell.
Restoration only takes place in pre-existing sanctuaries, as established by Maryland DNR. Sanctuaries are areas that are closed to harvest; however, oysters within sanctuaries are expected to increase the abundance of adult oysters whose larvae settle not only within the sanctuary, but also on public shellfish fishery areas in the vicinity of the sanctuaries.
Typically, there are two barges used for constructing the reefs: one barge holds the substrate (reef material, such as rock or mixed shell), the other holds a crane with a bucket to move the substrate. The bucket picks up the substrate from the barge, then, with a sweeping motion, releases it into the water. GPS locaters are used to make sure the reefs are constructed in the selected sites. Spat-on-shell are brought from hatcheries and placed or “planted” on the constructed reefs in hopes of restoring the oyster population in these areas. Once planted, the oyster reefs are monitored to assess the restoration progress.
The Corps is involved in oyster restoration in two ways. Through an authority under Section 704(b) of the Water Resources Development Act (WRDA) of 1986, as amended, the Corps provides construction assistance for certain oyster restoration projects through its Civil Works program. For work undertaken by others, the Corps evaluates the impact of material placed into Waters of the United States under Section 404 of the Clean Water Act and Section 10 of the Rivers and Harbors Act, through a permitting process managed by the Corps Regulatory Program.
The Maryland project cooperation agreement was executed in February 1997, with an amendment in July 2002. Placement locations in Maryland include Kedges Strait, Eastern Bay; and the Chester, Choptank, Magothy, Patuxent, Severn and Tred Avon rivers - a total of approximately 600 acres of new oyster bars. Some of the oyster bars were left for natural recruitment; others received hatchery-raised spat. The Virginia project cooperation agreement was executed in September 2001, with amendments in July 2004 and June 2007. The Corps' Norfolk and Baltimore districts support activities in Virginia and Maryland, respectively. In Virginia, activities include oyster bar creation in Tangier Sound, Pocomoke Sound, the Great Wicomico River, and the Lynnhaven River - a total of approximately 400 acres of new oyster bars.
Prior to the 2009 restoration activities, the Corps oyster restoration program did not focus on large-scale tributary restoration in Maryland, as it does now. From 1997 to 2006, the Baltimore District received relatively small funding allocations for a number of small sites, scattered throughout the Maryland portion of the Chesapeake Bay. An assessment of the sanctuary sites constructed during this period was prepared and can be found in the September 2011 report, 2008 Sanctuary Assessment.