The eastern oyster is one of the most famous and recognizable aquatic species in the Chesapeake Bay. For more than a century, oysters made up one of the Bay's most valuable commercial fisheries. The interaction of over-harvesting, disease, sedimentation and poor water quality has since caused a severe decline in their numbers throughout the Chesapeake.
While not everyone enjoys eating this peculiar-looking bivalve, we can all appreciate the vital functions oysters serve in the Bay's ecosystem, as well as their cultural and economic importance to the region.
Oysters provide underwater habitat in the form of aquatic reefs. With their many nooks and crannies, oyster reefs can create 50 times the hard surface area of an equally sized flat mud bottom. Hundreds of Bay creatures, including sponges, sea squirts, small crabs and many species of fish, need hard surfaces like those found on aquatic reefs to survive.
In addition to providing habitat, oysters are a source of food for a host of animals.
Oysters are filter feeders. This means that they feed by pumping large volumes of water through their gills and filtering out plankton and other particles. As they filter water to get food, oysters also remove nutrients, suspended sediments and chemical contaminants, helping to keep the water clear and clean for bay grasses and other underwater life. One oyster can filter more than 50 gallons of water per day.
The eastern oyster is a Chesapeake Bay icon. Since the late 19th century, the oyster industry — including the catch, sale, shucking, packing and shipping of oysters — has contributed millions of dollars to the region's economy and built a rich history and cultural heritage in the Bay region.
Scientists attribute the decline of the Bay's oyster population to a combination of several factors, including:
The decline in the Bay's native oyster population is often illustrated in terms of its impact on water quality: In the late 19th century, the native oyster population could filter a volume of water equal to that of the entire Bay every three to four days; today's depleted population takes nearly a year to filter the same volume.
Immense numbers of oysters existed in the Bay during colonial times. European settlers reported that huge oyster reefs thrusting up from the Bay's bottom posed navigational hazards to their ships. At the turn of the 20th century the Bay's oyster fishery was one of the most important in the U.S.
The Bay's oyster population has severely declined over the past century due to over-harvesting, which removed huge volumes of oysters. Over-harvesting also led to the demise of the Bay's healthy oyster reefs, which were scraped away by dredging.
Oyster beds are now usually limited to a flat, thin layer of dead shells and live oysters spread widely over the Bay's bottom. These damaged habitats:
In addition to harvest pressure, the Bay's oysters face a number of other challenges. One of these is disease. Since the 1950s, the oyster diseases MSX and Dermo have decimated the Bay's remaining oyster population.
The Bay's oysters have also been affected by poor water quality.
In 2005, the Chesapeake Bay Program adopted the 2004 Chesapeake Bay Oyster Management Plan, which provides Bay Program partners with a general framework and specific guidance for rebuilding and managing the Bay's native oyster population. The plan has four components: managing harvest, creating sanctuaries, overcoming the effects of disease, and using hatchery-reared seed.
However, it is important to note that the Bay's poor health is not due solely to a diminished oyster population and, therefore, cannot be corrected by restoring oysters alone. Other pressures on the Bay — such as polluted stormwater runoff from farms, cities and suburbs, and construction sites — must be addressed for oyster and water quality restoration efforts to be successful.
Oyster sanctuaries are aquatic reefs where shellfish harvesting is prohibited. Scientists often improve habitat in oyster sanctuaries by cleaning off sediment or adding cultch.
Decisions about where to locate sanctuaries are guided by the Virginia Oyster Restoration Plan, developed by the Virginia Institute of Marine Science (VIMS) and the Virginia Marine Resources Commission (VMRC); and by Maryland's Priority Restoration Areas, developed by the Maryland Department of Natural Resources (MD DNR) and the Maryland Oyster Roundtable Steering Committee.
The second component of the oyster management strategy implements harvest strategies to build a sustainable oyster industry in both Maryland and Virginia.
The main strategy for regulating harvest and enhancing harvest potential is to establish sanctuaries and special management areas throughout the Bay.
Management strategies for the Maryland oyster fishery are considered by a number of advisory groups working with MD DNR. In Virginia, oyster harvest is managed on a bar-specific basis.
The third component of the oyster management strategy recognizes the constraints of disease and implements management strategies that reduce the impact of disease.
Recently, it has been found that oysters in areas subject to high exposure to MSX are evolving to resist the disease. Scientists and managers are adjusting harvest and sanctuary management strategies to optimize the long-term benefits of the development of MSX resistance.
More than half of this season’s spat went into an oyster sanctuary on the Eastern Shore.
But a new report indicates oyster restoration could be more effective under stronger harvest limits.
For the second consecutive year, oyster abundance has increased in Maryland waters.
State and federal partners are working to restore oysters to 20 Chesapeake Bay tributaries by 2025.
Cages on private piers give spat a head start before they are planted in the Bay.
Oysters are one of the most recognizable species in the Chesapeake Bay, and one of the most important to the health of its ecosystem. Don “Mutt” Meritt from the University of Maryland explains the environmental role that oysters play and describes what scientists are doing to restore the iconic bivalve. Learn more about blue crabs in the Chesapeake Bay Program’s online Field Guide.
Produced by Steve Droter
Stock Footage: University of Maryland Center for Environmental Science, Horn Point Oyster Hatchery
Music: “A Moment of Jazz” by Ancelin
Publication date: June 01, 2006 | Type of document: Report | Download: Electronic Version
This report is the third in a series in which the Chesapeake Bay Environment Model Package was used to assess the environmental benefits of oyster restoration in the Chesapeake Bay. Here, the effects of oyster restoration to all potential…
Publication date: December 05, 2005 | Type of document: Report | Download: Electronic Version
The Oyster Management Plan includes both a general framework and specific guidance for managing and rebuilding the native oyster stock in Chesapeake Bay. The development of the plan was a multi-partner endeavor by representatives from state…
Publication date: September 01, 2005 | Type of document: Report | Download: Electronic Version
The Chesapeake Bay Environmental Model Package (CBEMP) was used to assess the environmental benefits of oyster restoration in Chesapeake Bay. The CBEMP consists of a coupled system of models including a three-dimensional hydrodynamic model,…
Publication date: April 01, 2005 | Type of document: Report | Download: Electronic Version
The Chesapeake Bay Environmental Model Package (CBEMP) was used to assess the environmental benefits of a ten-fold increase in native oysters in Chesapeake Bay. The CBEMP consists of a coupled system of models including a three-dimensional…
Publication date: January 10, 2005 | Type of document: Adoption Statement | Download: Electronic Version
An adoption statement signed by the Executive Council to continue the 2004 Oyster Management Plan. The 2004 Oyster Management Plan provides both a general framework and specific guidance for rebuilding and managing the native oyster,…
Publication date: August 14, 2003 | Type of document: Fact Sheet | Download: Electronic Version
While Chesapeake Bay Program partners continue their work to restore native oysters, efforts are also underway to better understand the risks and benefits surrounding the possible introduction of non-native oysters into the Bay. This…
Publication date: April 23, 2002 | Type of document: Fact Sheet | Download: Electronic Version
The purpose of this document is to communicate the findings and recommendations of the Federal Agencies Committee of the Chesapeake Bay Program with respect to an anticipated proposal to introduce the Suminoe oyster into the waters of the…
Publication date: March 01, 2000 | Type of document: Report | Download: Electronic Version
Report curtailing proceedings and agreement statements on oyster restoration derived from 2 day workshop held in Waldorf, MD on January 13 & 14, 2000. Contains important consensus statements derived from meeting, on oyster sanctuaries and…
Publication date: October 01, 1995 | Type of document: Management Plan | Download: Electronic Version
As part of the process of establishing accountability and tracking the implementation of management actions, each fishery management plan (FMP) is annually reviewed and updated. This report reviews the progress of management plans during…
Publication date: January 01, 1994 | Type of document: Management Plan
The goal of the 1994 Oyster Fishery Management Plan is to enhance the production of oysters in the Chesapeake Bay ecosystem by restoring habitat, controlling fishing mortality, promoting aquaculture and continuing the repletion programs.
Publication date: July 01, 1989 | Type of document: Management Plan
The purpose of the Plan is to manage the oyster resource by restoring oyster habitat, controlling fishing mortality, promoting aquaculture and continuing the repletion programs.