Public health protection is achieved as a result of sanitary surveys of shellfish growing areas to determine their suitability as shellfish sources for human consumption. The principal components of a sanitary survey include: 1) an evaluation of pollution sources that may affect an area, 2) evaluation of hydrographic and meteorological characteristics that may affect distribution of pollutants, and 3) an assessment of water quality.
Each growing area must have a complete sanitary survey every twelve years, a triennial evaluation every three years and an annual review in order to maintain a classification, which allows shellfish harvesting. Minimum requirements for sanitary surveys, triennial evaluations, annual reviews and annual water quality monitoring are established by the ISSC and set forth in the NSSP. Each year water samples are collected at 2,320 stations in 294 growing areas in Massachusetts's coastal waters at a minimum frequency of five times while open to harvesting. Two Marine Fisheries laboratories located in Gloucester and New Bedford test water and shellfish samples for fecal coliform bacteria using a membrane filtration method (mTEC agar) to determine the classification of shellfish growing areas and potential pollution sources.
Shellfish are also tested for various poisonous or deleterious substances based upon an assessment of pollution sources impacting growing areas as determined by the sanitary survey and also as a result of pollution events such as oil and chemical spills. Contaminants periodically recovered from shellfish include: hydrocarbons, heavy metals, pesticides and polychlorinated biphenyl's (PCB's). Action levels and Tolerances have been established by the U.S. Food & Drug Administration (FDA) for various contaminants to protect the public.
Besides protecting the public from shellfish borne fecal pathogens, another major aspect of the shellfish program involves monitoring for naturally occurring marine biotoxins produced by microscopic algae Alexandrium sp. the cause of paralytic shellfish poisoning (PSP) also known as "Red Tide". Consumption of shellfish containing certain levels of PSP toxin can produce severe illness and even death. Shellfish Program personnel collect shellfish from 15 primary or sentinel stations weekly from April through mid-November. Samples are sent to our Gloucester laboratory where bioassays determine the levels of toxin in the shellfish. If toxin is found, both the frequency of sampling and the number of sample sites are increased. Shellfish areas are closed if toxin levels exceed safe limits. In addition to bioassays, the Shellfish Program oversees a pilot phytoplankton monitoring program under a grant from the U.S. FDA, Office of Seafood. "Volunteers" (mostly local shellfish department personnel or others with strong biology backgrounds) trained and equipped with field microscopes and plankton nets by MarineFisheries and FDA, collect and analyzed hundreds of phytoplankton samples. The purpose of this program is to augment the shellfish analysis by providing early warning of potentially toxic blooms besides Alexandrium such as Dinophysis and Psuedonitzchia and to expand the number of sites being monitored along the coast.
Another component of the sanitation program involves maintaining a direct link with the state Department of Public Health (DPH) on all matters related to shellfish safety and public health protection. MarineFisheries provides information regarding harvest area status and assists DPH in tracing the source of shellfish in commerce. We also aid DPH in the regulation of shellfish wet storage by wholesale dealers. Plus, Shellfish Program personnel certified by FDA as Laboratory Evaluation officers, evaluate non-state laboratories that conduct shellfish related analyses.
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