Shellfish Restrictions and Closures Currently in Effect
November 4, 2008Shellfish Growing Area Monitoring Program
The Shellfish Growing Area Monitoring Program is part of the State of Rhode Island’s agreement with the United States Food and Drug Administration’s (FDA) National Shellfish Sanitation Program. The purpose of this program is to maintain interstate certification of these waters for shellfish harvesting for direct human consumption through continuous bacteriological monitoring of shellfish harboring waters. Analyses and results ensure maintenance of industry health standards. Shoreline surveys are required every 1, 3 and 12 years to reassess shellfish classification in growing areas and to locate all actual and potential bacterial sources along the shoreline.
Rhode Island collects samples from 17 separate shellfish growing areas. These growing areas encompass all shellfishable marine waters of the state. Each of the growing areas incorporate anywhere from 9 to 39 fixed sampling stations.
After collection, bacterial water samples are returned to the RI Department of Health laboratory for analysis. The results of this analysis are reported as the most probable number (MPN) of total and fecal coliform bacteria. Fecal coliforms are found in wastes from warm-blooded organisms. These bacteria are non-disease causing but they serve as an indicator organism for the possible presence of other potentially pathogenic, sewage-associated microorganisms. These microorganisms can cause diseases such as cholera, hepatitis, and gastroenteritis and can be contracted by consuming sewage-contaminated shellfish. The State retains its certification for interstate sale of shellfish by restricting shellfish harvesting to those areas that maintain total and fecal coliform levels below specific statistical parameters established by the State and agreed to by the Food and Drug Administration (FDA). Rhode Island, with the consent of the FDA, recognizes the following six different classifications of shellfish growing areas:
Approved - This status allows unrestricted harvesting of shellfish (unless restricted by conservation closures) for direct human consumption and is only allowed in areas free from harmful levels of pollution.
Conditionally Approved/Seasonal - This status prohibits shellfishing only during the summer months (Memorial Day weekend through Columbus Day weekend) due to the potential pollution from concentrations of boats with marine toilets during the boating season, and also areas with elevated bacteriological levels due to suspected nonpoint septic system leachate from summer residences.
Conditionally Approved - These areas change in quality due to rainfall-related problems such as combined sewer overflow discharge and/or sewerage system failures. These areas are from time to time found to be in an unsatisfactory condition for the taking of shellfish for human consumption and are then declared to be polluted and closed. In most cases, closure for seven days occurs following a rain event of greater than 0.5” within a 24-hour period in the Providence area.
Prohibited - This status prohibits the harvesting of shellfish on a year-round basis due to the presence of pollution during significant periods of the year.
Conditionally Restricted - These areas are used for shellfish relays only.
Remote - These areas have no human habitation and are not impacted by any actual or potential pollution sources. Areas can be closed for management purposes or due to heavy bacteriological load.;)
Fig. EW 7. Shellfish restriction Areas for Narragansett Bay. Based on RIDEM Water Resources maps.
Water samples are collected monthly at the stations in the Upper Narragansett Bay (the area north of Prudence and south of Conimicut). During wet weather, increased sample runs are completed to ensure that bacterial quality has returned to acceptable levels in conditionally approved areas. Area A, the northern portion of the Upper Bay, is closed for a period of seven days following rainfall events of 0.5” or greater. Area B, the southern portion of the Upper Bay, is closed for a period of seven days following rainfall events of 1” or greater. Both areas are closed for ten days following a rainfall event of greater than 3” (Fig. EW 7).
Greenwich Bay, Mount Hope Bay and the Kickemuit River have been operating on a conditionally approved basis for the past several years and are sampled monthly when they are open for shellfishing. These areas are closed for a period of seven days following a wet weather event totaling 0.5” or greater. Growing areas are sampled at the same time, and the results are used to manage the conditionally approved shellfish growing areas of Mount Hope Bay and the Kickemuit River.
The portions of Greenwich Bay that are not permanently closed are managed as a conditional closure. The central portion of the bay is managed as a seasonal closure area and is closed from Dec 1- Feb1 due to high bacteriological samples, possibly due to rainier winters. Between Dec 1 and Feb1, an eastern portion of the bay is managed as a conditionally approved area with closures after rainfall events of 0.5” or greater. The conditionally approved waters of Greenwich Bay are also an official management area overseen by the Division of Fish and Wildlife. Further details on management closures can be found on the DEM’s Fish and Wildlife web site. Pollution closures supercede management closures. The closure rates for the conditionally managed areas in the Upper Narragansett Bay (Fig EW 8. a and b) closures for Greenwich Bay and the Mt. Hope Bay and Kickemuit River are shown in Fig. EW 8b.
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ig. EW 8a. Percent of Year Upper Bay Areas A & B of the Bay are closed vs. Annual Precipitation. ;)
Fig. EW 8b. Percent of Year Greenwich Bay, Mount Hope/Kickamuit Conditional Areas are closed vs. Annual Precipitation.
The other shellfish growing areas in Rhode Island are not subject to the volume and number of sewage discharges that affect the Upper Narragansett Bay, or the predictable nonpoint source impact that affects Greenwich Bay, the Kickemuit River and Mt. Hope Bay. Accordingly, these other shellfish growing areas are monitored less frequently. In March 1981, the sampling program was expanded from regularly scheduled monitoring of just the Upper Bay to regular monitoring of all shellfish growing areas of the state in order to maintain interstate certification. More recently, the emphasis has shifted to a trend-oriented monitoring program based on a random date sampling methodology developed by the FDA. At present, growing areas that are approved for shellfish harvesting are sampled a minimum of six times a year. An attempt is made to sample growing areas a minimum of once a year where shellfish harvesting is prohibited. Due to the lack of potential pollution sources impacting the Off Shore growing area, it is classified as remote and therefore is required to be sampled only twice a year.
Changes in Shellfish Growing Area Status
DEM announces seasonal shellfish closures and any changes to shellfish closure status annually in May. The seasonal closures are made every year during the summer months because of increased marine activity. In addition to seasonal closures, DEM announces classification changes made based upon the results of the Department’s routine monitoring program. The changes made for the calendar years 1986-2005 are shown in Fig. EW9 and a summary of changes in shellfish growing areas and their classification is listed in Table 1.
Fig EW 9. Changes in status in shellfish growing areas vs. annual precipitation.
In 1986, a total of 1081 acres were newly restricted. 355 acres were due to increased boating use in Great Salt Pond resulting in a change from approved to conditionally approved/seasonal. 615 acres of the other closures were due to exceedance of bacteriological monitoring results in the Pettaquamscutt River and Bristol Harbor areas. A total of 687 acres were closed to shellfishing in 1987, mainly due to exceedances of shellfish standards during the summer season at Green Hill Pond and the discovery of point source discharges in the Sakonnet River area.
In June 1990, the conditional area of Upper Narragansett Bay was divided into Areas A and B, due to better water quality in the southern portion of the Bay. This allowed the southern portion (Area B) to remain open to shellfishing during rainfall events up to one inch and resulted in fewer closures in that area of the Bay. In August 1991 a statewide shellfish closure occurred following Hurricane Bob. All areas were reopened to shellfishing within nine days.
Due to a series of winter storms in 1992, 2543 acres of Greenwich Bay were closed indefinitely due to an exceedance of bacteriological monitoring standards. The FDA was enlisted to conduct a comprehensive sanitary survey of Greenwich Bay during the spring and summer of 1993 and this survey was used to develop an operating procedure for managing the bay as a conditionally approved area. In 1994, Greenwich Bay was reopened to shellfishing as a conditionally approved area. In 1995, 2265 acres of the Mount Hope and Kickemuit River area were changed from prohibited to conditionally approved due to the results of a study that determined the area could be managed on a conditionally approved basis.
New closures have tended to remain low since 1993, with the closure rates of conditionally approved areas such as Upper Narragansett Bay tracking closely with rainfall, which drives these closures. In 1995, 6505 of the 6929 acres closed were due to the enlargement of official dilution buffer zones around all wastewater treatment facilities (WWTFs), as well as closure of a portion of the Upper Point Judith Pond and Hundred Acre Cove in the Barrington River (370 acres).
Maps and descriptions of the Shellfish Closure Areas can be found on the DEM website. It is important to note that some of the closed shellfish areas shown on the Shellfish Closure Area maps include waters that are not designated as shellfishing areas. Incorporating these areas into the description of shellfish closure areas allows for siting of enforceable shellfish closure lines and for ease of informing the public via maps of closed areas, whether the closure is due to pollution or a designated classification.