Deadly Toxin Closes Shellfishing in R.I., Mass. Waters

By ecoRI News staff

Key shellfishing locations in both Rhode Island and Massachusetts waters have been closed because of the presence of toxic phytoplankton.

On Oct. 7, the Rhode Island Department of Environmental Management (DEM) closed several areas of Narragansett Bay to shellfish harvesting until further notice. The confirmed harmful algae bloom (HAB) is the first HAB-related shellfishing closure in Rhode Island.

Impacted waters extend from the mouth of Narragansett Bay to Conimicut Point. This area includes Narragansett Bay, Greenwich Bay and all tributaries to those waters north of a line from the point just north of the Pettaquamscutt (Narrow) River at Cormorant Point to Beavertail Point in Jamestown to Brenton Point in Newport and south of a line from the Old Tower at Nayatt Point to the DEM range marker at Conimicut Point.

A day later, on Oct. 8, DEM announced shellfishing was also prohibited in all waters of Mount Hope Bay, Kickemuit River and the Sakonnet River north of a line from Sachuest Point in Newport to Sakonnet Point in Little Compton. All tributaries to those waters also are restricted.

Given the high concentrations of phytoplankton in several areas, the Massachusetts Division of Marine Fisheries (DMF) has banned the harvesting of shellfish in Buzzards Bay, Mount Hope Bay and Lackeys Bay. As a result of the closure, digging, harvesting, collecting and/or attempting to dig, harvest or collect shellfish, and the possession of shellfish, is prohibited in Bourne, Dartmouth, Fairhaven, Falmouth, Gosnold, Marion, Mattapoisett, New Bedford, Swansea and Westport.

DMF staff will continue testing the waters of Vineyard Sound, Nantucket Sound and Cape Cod Bay for the presence of the toxin.

DEM, in partnership with the Rhode Island Department of Health, also will continue to collect local shellfish for analysis to determine if the toxins are present in shellfish meats at levels of concern. The toxin, known as domoic acid, produced by these phytoplankton is responsible for causing amnesiac shellfish poisoning in humans.

The shellfishing closures in both Rhode Island and Masschusetts were caused by the presence of toxic phytoplankton, Pseudo-nitzschia spp. Several species of Pseudo-nitschia produce the toxin domoic acid, according to the National Oceanic and Atmospheric Administration (NOAA).

Amnesic shellfish poisoning produces gastrointestinal and neurological effects. Mild cases arise within 24 hours of consumption of contaminated shellfish, according to NOAA. Symptoms include nausea, vomiting, diarrhea and abdominal cramps. In more severe cases, neurological symptoms occur, including headaches, hallucinations, confusion, short-term memory loss, respiratory difficulty, seizures, coma and, in extreme cases, death.

Amnesic shellfish poisoning was recorded for the first time off the Atlantic coast of Canada in 1987 when three deaths and more than 100 confirmed cases of acute intoxications followed the consumption of cultured mussels.

Update: Effective at noon Oct. 15, all waters impacted by the precautionary shellfish harvesting closure in Rhode Island were open to shellfishing, with the exception of conditional areas which remain closed due to rainfall and are scheduled to reopen at noon on Oct. 17.