Fears of “red tide” contamination have prompted state officials to close New Hampshire’s coastal waters to shellfish harvesting, including mussels, clams and oysters.

The state’s Department of Environmental Services and the Fish and Game Department announced the closure to protect the public from possible consumption of contaminated shellfish.

It came after elevated levels of paralytic shellfish poisoning (PSP), commonly known as “red tide,” were detected in blue mussels collected from Hampton/Seabrook Harbor last week.

The closure applies to Atlantic coastal waters as well as the waters of Hampton/Seabrook Harbor. “Red tide toxicity levels are increasing right now in the Gulf of Maine and in Hampton/Seabrook,” said Chris Nash, shellfish program manager for NHDES. “It is too soon to know how severe this algae bloom will be or how long it might last.”

Other New Hampshire shellfish harvesting areas, including the recreational oyster beds around Nannie Island and Adams Point in Great Bay, and the commercial oyster farms in Little Bay, are not affected by this closure.

The red tide closure also does not apply to the harvest or consumption of lobster, although state officials continue to advise consumers to avoid eating tomalley, which is a lobster’s digestive gland.

Weekly sampling will continue until October, Nash said. Changes to the open/closed status of shellfish waters will be announced on the Clam Flat Hotline (1-800-432-5267) and on the NH Coastal Atlas website: https://www4.des.state.nh.us/CoastalAtlas/Atlas.html.

Red tide is a condition in which filter-feeding shellfish such as clams, oysters and mussels accumulate a potent neuro-toxin produced by a naturally-occurring marine algae.

Ingesting the toxin is potentially fatal to humans, and cooking does not make contaminated shellfish safe for consumption.

For more information, consult the NHDES Shellfish Program website: https://www.des.nh.gov/organization/divisions/water/wmb/shellfish/index.htm.