Bay Program partners developed the Chesapeake Bay Oyster Management Plan to help restore and maintain the valuable ecological services provided by native oysters while continuing to support an oyster fishery. The strategy described in the Oyster Management Plan consists of three components: Defining oyster sanctuaries, managing harvest and overcoming the effects of disease.
Chesapeake Bay Oyster Restoration
However, it is important to understand that the Bay's poor water quality is not due solely to the loss of the oyster population and, therefore, cannot be corrected by restoring oysters alone. Other pressures on the Bay's ecosystem—including land use practices and nutrient and sediment pollution—must be addressed for future oyster and water quality restoration efforts to be successful.
Oyster Sanctuaries
The first component of the oyster management strategy defines sanctuaries—areas where harvesting is prohibited—to increase the ecological function of oyster beds.
Scientists also improve habitat in these areas by cleaning sediment off the reefs and adding cultch (clean, empty shells or other hard material) for new spat to settle on.
By restoring oyster reefs and protecting them from harvest, there is potential to increase populations of spawning adult oysters and, in turn, larval production.
In the short term, factors like disease and water quality will significantly limit the success of oyster sanctuaries and the increase in oyster populations; however, sanctuaries will become important contributors to oyster restoration if disease resistance is allowed to evolve over time in wild populations and is supported by management practices.
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.
Managing Oyster Harvest
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.
The ideal situation is to estimate the amount of oysters that can be taken safely from the population while maintaining a sustainable Bay-wide population of oysters.
A major challenge is to determine what level of exploitation is appropriate and will not compromise restoration efforts.
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.
Oyster Disease
The third component of the oyster management strategy recognizes the constraints of disease and implements management strategies that reduce the impact of disease.
A major challenge to oyster restoration in the Bay is to overcome the effects of the diseases MSX and Dermo. It is estimated that, by age 3, 80 percent or more of a year class in high disease areas (i.e., the Virginia portion of the Bay) will die due to disease.
Maryland and Virginia confront different problems concerning disease. Virginia oysters are faced with constant disease pressure because MSX and Dermo thrive in warmer, saltier waters. Maryland's situation is more variable depending on weather conditions.
Research efforts have been underway for a number of years to breed strains of native oysters with greater disease resistance. Current research will give scientists a better understanding of how these disease-tolerant strains could contribute to large-scale oyster restoration efforts.
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.
Introduction of a Non-native Oyster
In response to the decline in the native oyster population, Maryland and Virginia have proposed intentional introduction of a non-native oyster species, Crassostrea ariakensis (also known as Suminoe or Asian oyster). This species is believed to have greater resistance to MSX and Dermo.
Considerable controversy exists over this proposal, and many questions remain about the possible implications of introduction. In 2003, the U.S. Congress mandated that an environmental impact statement (EIS) be prepared to examine both the risks and benefits of introducing this species to the Bay, compared with the risks and benefits of other management alternatives. A draft EIS is expected to be released in 2008.
In 2004 the National Research Council of the National Academies published its year-long study, Nonnative Oysters in the Chesapeake Bay. This independent study is the most complete analysis to date on the possible introduction of non-native oysters into the Bay.
According to the study, introduction of a non-native oyster should be delayed until more is known about the environmental risks. However, carefully regulated cultivation of sterile Asian oysters in contained areas could help both researchers and the Bay's oyster industry.
The study also noted that it could take decades before there are enough oysters to improve water quality. While Asian oysters would filter excess algae from the water, they would not be a “quick fix” to restore water quality.
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