Oyster populations show improvement in Maryland sanctuaries, study finds

Oyster populations throughout Maryland’s portion of the Chesapeake Bay have generally improved over the past decade, according to a report from the state’s Department of Natural Resources (DNR). But while oysters within state-designated sanctuaries have continued to thrive in recent years, populations in areas open to harvest have declined.

Three types of oyster management areas are designated in Maryland: active aquaculture, or oyster farming; sanctuaries, where harvesting is not allowed; and Public Shellfish Fishery Areas, or PSFAs, which are open to public harvesting.

Low disease mortality combined with successful reproductive seasons in 2010 and 2012 helped boost populations of the Bay’s iconic bivalve in both fished and sanctuary areas. But as oyster biomass in sanctuaries continued to increase through 2014 and 2015, populations in areas open to fishing declined in those years. According to the report, this is likely due to the harvest of those oysters born in 2010 and 2012—inside the sanctuaries, these older oysters were continuing to grow and reproduce.

In 2010, Maryland adopted an updated oyster management plan, expanding the range of sanctuaries and designating areas to remain open to harvest. The study marks the first evaluation in DNR’s commitment to review the plan’s effectiveness every five years and to propose adjustments if necessary. But the report suggests it’s too early to conclude that oyster restoration efforts have been successful.

“Given the complexity of the Chesapeake Bay ecosystem, five years has not been long enough to show how oyster populations respond to the absence of harvest,” the report states. Still, the report recommends making adjustments to current sanctuary boundaries, while continuing to maintain sanctuaries in 20 to 30 percent of the Maryland portion of the Bay.

The State Oyster Advisory Commission, a 23-member group created to advise DNR on oyster-related matters, is expected to review the report and make recommendations on the state’s oyster restoration efforts, including postponed work in the Tred Avon River.

The report is available on the Maryland Department of Natural Resources website.