Red tide has hit Cape Ann, and the state has banned shellfishing in Gloucester, Essex and Rockport until further notice.
The state’s Division of Marine Fisheries on Thursday banned harvesting of all bivalve shellfish and carnivorous snails in the Annisquam River and Gloucester Harbor, said Gloucester shellfish warden Peter Seminara. It had already banned shellfishing in Essex Bay earlier this week.
Also off limits to the harvesting of blue mussels, ocean quahogs and carnivorous snails are the waters, tributaries and flats off Ipswich, Rowley, Newbury, Newburyport and Salisbury. Locally, the areas in question are N:1-6, N:8, and N:10-14.
This move was in response to elevated levels of paralytic shellfish poisoning, commonly known as red tide, found in a variety of shellfish. Filter-feeding soft-shell clams, blue mussels, ocean quahogs, carnivorous snails, and other bivalve shellfish accumulate the potent neurotoxin, which is produced by a naturally occurring marine algae.
Fried Essex clams are a specialty for local restaurants, and many, including Woodman's of Essex, have a fallback plan in case reserves run low, according to a spokesman.
Rockport Shellfish Constable Scott Story said he does not know how long the red tide is sticking around.
"It's all up to the dinoflagellates," he said, referring to the single-cell organisms involved in red tide. Large groups of them cause seawater to appear red. "It all depends on the nutrients available to them and the temperature of the water."
Seminara said the state is expected to retest for the toxin on Monday, and the results should be announced later in the week.
Eating contaminated shellfish is potentially fatal to humans, and cooking does not eliminated the danger.
Red tide does not pose a threat to swimmers and beachgoers, Seminara said.