Maryland Shellfish Harvesting Areas

    ●  Daily Advisory on Conditionally Approved Shellfish Harvesting Areas

Maryland's Chesapeake Bay waters have long been known for their plentiful shellfish. To protect this valuable resource and safeguard public health the Maryland Department of the Environment is responsible for regulating shellfish harvesting waters.

Shellfish include clams, oysters, and mussels. The term shellfish does not include crabs, lobsters, or shrimp. Shellfish are filter-feeding animals: they strain the surrounding water through their gills which trap and transfer food particles to their digestive tract. If the water is contaminated with disease-causing bacteria, the bacteria are also trapped and consumed as food. If shellfish are harvested from waters which the Department has restricted (closed) and eaten raw or partially cooked, they have the potential to make people sick. Therefore, it is mandatory for oysters and clams to be harvested from approved (open) shellfish waters only.

Shellfish harvesting waters which are open or approved for harvesting are those where harvesting is permitted anytime. Areas which are conditionally approved mean that shellfish harvesting is permitted except for the three days following a rain event of greater than one inch in a twenty-four hour period. Runoff from such a rainfall can carry bacteria into surface waters from adjacent land. Information about which areas have conditional closures is updated daily on the web and via a recording. Click here to find out which conditional closures are in effect or call 1-800-541-1210.

MDE's Water and Science Administration (WSA) is responsible for regulating shellfish harvesting waters. This effort has three parts: 1) identifying and eliminating pollution sources, 2) collecting water samples for bacteriological examination; and 3) examining shellstock samples for bacteriological contamination and chemical toxicants.

Sanitary Surveys

Maryland Department of the Environment’s (MDE) conducts sanitary surveys of each shellfish harvesting area prior to its approval as a source of shellfish for the consumer. The purpose of the sanitary survey is to identify and evaluate factors influencing the sanitary quality of a shellfish harvesting area. These factors may include sources of potential and actual pollution (failing septic systems, animal wastes from agricultural properties, wastewater treatment plants, industrial waste, surface-runoff from polluted areas), bacterial quality of the water and shellfish, hydrographic characteristics of shellfish harvesting areas, and general land-use patterns.

Data gathered during the sanitary survey are used to evaluate the shellfish harvesting area and to determine whether a health risk exists. If no health risk is apparent, the area remains open to shellfish harvesting. When the data indicates a health risk, the area is restricted to the harvesting of shellfish. Through the efforts of this extensive program, Maryland has enjoyed an excellent reputation as a source of safe and wholesome shellfish products to seafood lovers throughout the nation and the world.

Maryland's Shellfish Harvesting and Closure Area Maps

These maps summarize the Maryland Department of the Environment’s (MDE) classification status of oyster & clam harvesting waters as of March 31, 2014.  The maps depict the classification of shellfish growing waters of the State as restricted, conditionally approved, seasonally conditionally approved or approved. 

Also shown in the maps are Shellfish areas closed as reserves and sanctuaries by the Department of Natural Resources (DNR).  Sanctuaries are areas which are closed to shellfish harvest and often contain oyster restoration projects to help enhance oyster populations for their environmental benefits.  These areas are permanent closures.  Reserves are areas which are restored, then opened for periodic harvest when certain criteria are met.

Mapping Information

Contact Information

For more information concerning shellfish harvesting, contact MDE's Water and Science Administration(WSA) at (410) 537-3608 or the Natural Resources Police at (410) 260-8880. For interstate shellfish sanitation information, visit

Fact Sheets

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