Maine Shellfish Growing Area Classification Program
Anna Bourakovsky, Boothbay supervisor, field work 
Robert Goodwin, Lamoine supervisor, field work
Mercuria Cumbo, supervisor, lab work
Program Description
The Growing Area Classification Program evaluates all shellfish growing areas in the state of Maine to determine their suitability of harvest. See Maine Shellfish Growing Area Reports.
This program is guided by the NSSP standards. Please select this link to find the 2005 NSSP Guide for the Control of Molluscan Shellfish (commonly called the "Model Ordinance").
Because molluscan shellfish (those that have a hinged shell, such as clams, mussels, oysters, quahogs, etc.) are filter feeders, the quality of the waters in which they grow is a key factor in determining whether they are safe to eat.
Growing Area Classifications
A growing area's classification is determined by conducting a "sanitary survey," which is a three-fold process consisting of:
• A shoreline survey, which identifies pollution sources that may impact water quality. The program evaluates sewage treatment plants, onsite sewage systems, animal farms, drainage ways, and wildlife;
• Marine water sampling to determine fecal coliform bacterial levels in the marine water; and
• Analysis of how weather conditions, tides, currents, and other factors may affect the distribution of pollutants in the area.
Each commercially harvested growing area is assigned a "classification" according to the results of its evaluation. A growing area may be classified as one of these:
• Approved
• Conditionally Approved
• Restricted
• Conditionally Restricted
• Prohibited.
A growing area may be classified as Approved when the sanitary survey shows that the area is not subject to contamination that presents an actual or potential public health hazard.
An Approved classification authorizes shellfish harvest for direct marketing.
A growing area may be classified as Conditionally Approved when it meets Approved criteria, but only during predictable and manageable periods. For example, during dry weather a growing area may meet Approved water quality standards, but after a certain amount of rain falls (termed a "rainfall event") the water quality declines. In this example, the Conditionally Approved area is temporarily closed to harvest after a rainfall event. The length of closure is determined for each Conditionally Approved area, and is based on water sample data that show the amount of time it takes for water quality to recover and again meet Approved criteria. Once the water quality returns to Approved criteria, the area is reopened.
A Restricted classification is used for areas that do not meet water quality standards for an Approved classification, but the sanitary survey indicates only a limited degree of pollution. Shellfish harvested from Restricted growing areas cannot be marketed directly. They must be “relayed” or “depurated”. Shellfish that are “relayed” are moved to Approved growing area waters for a specified amount of time, allowing shellfish to naturally cleanse themselves of contaminates before they are harvested for market. Shellfish that are “depurated” are moved to a depuration facility to cleanse themselves in sterile seawater under strict controls and are tested before they are released to the market. Shellfish harvesting in a Restricted area requires a permit: for an application, go to Maine Department of Marine Resources, Public Health Division - Shellfish Program and look under Forms.
A growing area may be classified as Conditionally Restricted when it meets Restricted criteria, but only during predictable and manageable periods. For example, a Restricted area that is adjacent to a sewage treatment plant Prohibited area may meet Restricted water quality standards, but after a malfunction at the sewage treatment plant the water quality declines. In this example, the Conditionally Restricted area is temporarily closed to harvest after a sewage treatment plant malfunction. The length of closure is determined for each Conditionally Restricted area, and is based on water and shellfish tissue sample data that show the amount of time it takes for water quality and the shellfish to recover and again meet Restricted criteria. Once the water quality and shellfish return to Restricted criteria, the area is reopened.
Shellfish harvested from Conditionally Restricted growing areas cannot be marketed directly. They must be “relayed” or “depurated”. Shellfish that are “relayed” are moved to Approved growing area waters for a specified amount of time, allowing shellfish to naturally cleanse themselves of contaminates before they are harvested for market. Shellfish that are “depurated” are moved to a depuration facility to cleanse themselves in sterile seawater under strict controls and are tested before they are released to the market. Shellfish harvesting in a Restricted area requires a permit: for an application, go to Maine Department of Marine Resources, Public Health Division - Shellfish Program and look under Forms.
A growing area must be classified as Prohibited when the sanitary survey indicates that fecal material, pathogenic microorganisms, or poisonous or harmful substances may be present in concentrations that pose a health risk to shellfish consumers. Growing areas adjacent to sewage treatment plant outfalls, licensed overboard discharges, and other persistent or unpredictable pollution sources are classified as Prohibited. Growing areas that have not undergone a sanitary survey are also classified as Prohibited. Shellfish harvests are not allowed from Prohibited areas.
Once classified, all shellfish growing areas are regularly monitored. Marine water samples are collected throughout the year. Shoreline surveys are conducted less frequently, but each year some portion of the Maine coast (47 shellfish growing areas) are surveyed. During those surveys, all actual and potential pollution sources that may impact water quality are evaluated.
The purpose of continued water sampling and shoreline surveys is to ensure that growing areas continue to meet the standards associated with their classification, to modify classifications when needed, and to notify the responsible agencies about identified and potential pollution sources.
The PDF files below require Adobe Acrobat or the free Adobe Reader (download here). If you need an alternate format, please contact Michelle Mason.
Field Component
Laboratory Component
Maine Growing Area Classification Legal Notices Inventory
Reports and Studies
Resources and Educational Material for Municipalities and Industry
