Oysters are currently at historic low abundance due to disease-related mortality, habitat degradation, reduced water quality and harvest pressure. Based on recent scientific review of restoration alternatives for the native oyster in Chesapeake Bay, the ecological restoration team works with our many partners to optimize ecological benefits and enhance population recovery while minimizing costs. We work closely with our partners to rehabilitate degraded habitat using natural oyster shell and/or alternate substrates and to target the planting of hatchery-produced oysters. Please explore this page to learn more about our restoration activities.
Targeted Restoration
Recent bottom survey data, oyster population surveys and water quality data along with historical oyster bar locations are used to help determine the best sites for restoration. Knowing the salinity patterns in a tributary allows us to select a restoration approach that appropriately addresses disease and recruitment issues for each tributary. Although successful recruitment occurs in higher salinities, oysters there may be subject to greater disease pressure. Conversely, oyster populations in lower salinities experience less disease pressure but are recruitment-limited and may suffer from freshet mortality. Many partners, including federal and state agencies, non-profit organizations and educational institutions are involved in completing any one project.
Facing a Shell Shortage
Oyster shell is the predominant and preferred cultch for oyster habitat projects in the Bay. One major source are shucked shells from processing plants either in-state or out-of-state. The volume of shells varies annually due to changing harvest levels. Another source of shucked shells are restaurants, festivals and the general public all who recycle shells as part of an organized program to collect shells to prevent them from going to landfills. The annual volume of recycled shells is relatively small but it is still an important source. Historically in Maryland shells were also available from buried deposits in the upper bay (dead oyster bars). A large- scale shell dredging program from 1960-2006 was the dominant source of shells for that time period, far exceeding the volume of shucked shells. However, permit issues and a reduction in shell dredging sites resulted in an end of the program in 2006. Dredged shells are no longer available in Maryland. Shells are vital for oyster restoration and industry enhancement but improving degraded oyster habitat across large areas will require more shell than is available.
Alternative Substrates
Because of the shortage of oyster shell, Maryland is using alternate substrates to rebuild degraded oyster bars. Clam shell, mixed shell (clam, conch and whelk), fossil oyster shell from out-of-state and granite are some options to provide a firm base for the placement of spat-on-shell. These materials have proven effective not just as a base for spat on shell, but also for the settlement of natural oyster larvae.
Oyster Hatcheries
In order to meet the demands of an aggressive restoration agenda and a rapidly growing Marylanders Grow Oysters program, Maryland must have access to large quantities of oyster larvae (over 2 billion per year) for restoration. Larvae produced in hatcheries are released into large tanks, which are filled with shells. The larvae settle upon the shells creating spat-on-shell (baby oysters), which is then planted on various restoration sites.
Image of spat-on-shell.
(Photo credit: http://hatchery.hpl.umces.edu/purchasing-information/spat-on-shell-sales/)
Tributary-Scale Projects
As a part of the 2014 Chesapeake Bay Watershed Agreement, Maryland committed to restoring oyster populations in five tributaries in Maryland’s portion of the Chesapeake Bay by 2025. The tributaries chosen for restoration are Harris Creek, Little Choptank, Tred Avon, Upper St. Mary’s and Manokin Rivers.
Next Large-Scale Restoration Projects
As the oyster goal of restoring five tributaries is realized, the department adopted the Four Point Sanctuary Plan , to continue the success of large-scale restoration in additional sanctuaries. The department worked with the Oyster Advisory Commission to acquire feedback on choosing the next areas to focus the large-scale restoration efforts. The sanctuaries chosen as the next large-
scale restoration areas are the Nanticoke River, Herring Bay and Hooper Strait sanctuaries.
Small-Scale Projects
In a December 15, 2017 press release, DNR announced the intention to design and develop oyster management plans for restoration efforts in sanctuaries in addition to the five tributaries. Specifically, the press released stated the Nanticoke and Severn rivers would have plans developed to determine how the strategic use of state investment and resources could restore oyster populations, using planted seed, shell and spat to spur natural oyster growth and reproduction.
In a September 5, 2018 press release, DNR announced the intention to study and survey existing state oyster sanctuaries in Anne Arundel County, including the Severn River Sanctuary and to work with the local watershed associations to maximize the restoration potential in the tributaries.
Additional Restoration Projects
