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New Hampshire Department of Environmental Services

Media Center

DATE: October 2, 2020
CONTACT: Chris Nash, NHDES Shellfish Program, (603) 568-6741

Cold Weather Ban on Shellfish Harvest in Little Bay and Bellamy River to be Partially Lifted

Concord, NH - Effective October 1, 2020, the New Hampshire Department of Environmental Services (NHDES) and the New Hampshire Fish and Game Department announce that the cold weather ban on harvest of shellfish in Lower Little Bay and the Bellamy River will be partially lifted, due to improvements at the newly-upgraded Portsmouth municipal wastewater facility. A precautionary ban on all shellfish harvest for the months of October-March was first implemented October 2018 – March 2019, and again for the period of October 2019-March 2020. The ban was in response to potentially high virus levels, such as norovirus and hepatitis, in wastewater from the old Portsmouth municipal wastewater facility, which was not employing advanced wastewater treatment. The City recently completed an upgrade to the old facility, and has been operating with advanced treatment since April 2020. Ongoing effluent testing by NHDES has shown consistently low virus levels in effluent. This partial lifting of the ban on cold-weather harvest will increase recreational shellfish harvest opportunities, and will allow commercial oyster farms to operate well into the fall and winter. NHDES communicates daily with the shellfish industry and the NH Fish and Game Department on when water quality meets standards for shellfish consumption.

The reason for the precautionary ban dates back to the 2018 completion of a multi-year study of Portsmouth wastewater effluent and its effects on estuarine water quality and shellfish. The study found very high levels of virus indicator in effluent discharged to the Piscataqua River, much higher than what is discharged from other Seacoast wastewater facilities. The study also examined how virus levels vary throughout the year in the effluent, in Piscataqua River and Little Bay seawater, and in shellfish tissues throughout the estuary. Study results showed that virus particles are present throughout the year in the effluent, but because of the effects of various summertime factors like sunlight/ultraviolet radiation, viruses do not persist in the environment during the warmer months. However, as fall transitions to early winter, the virus particles from the effluent do persist in the seawater entering Little Bay. The tests on the shellfish tissues from multiple years confirm that the shellfish accumulate the virus particles in their tissues at significant levels. High virus indicator levels suggest that other disease-causing viruses such as norovirus and hepatitis might be present. NHDES deemed this to be an unacceptable public health risk for those who would eat those shellfish harvested during these cold-weather months. Thus, a precautionary closure for the months of October through March, affecting commercial and recreational shellfish harvest in Lower Little Bay and the Bellamy River, was implemented. Commercial and recreational harvest in other areas such as Upper Little Bay and Great Bay was not affected by the precautionary closure.

In late 2019, the City of Portsmouth completed construction of a new wastewater treatment facility, which has been operational since April 2020. NHDES, in cooperation with the City of Portsmouth and the NH Department of Health and Human Services Public Health Laboratory, has been testing treated wastewater from the new facility on a weekly basis since late April 2020. "Our testing so far has demonstrated that the new Portsmouth facility is very efficient at removing virus indicators from the wastewater. The fully treated wastewater being discharged to the Piscataqua River is consistently below the detection limit of the laboratory test," said Chris Nash, Shellfish Program Manager for NHDES. Nash explained that the precautionary ban could only be partially lifted at this time, because very little testing of the new Portsmouth facility has been done under wet weather conditions. "Our evaluations of other seacoast facilities show that when a wastewater treatment facility is experiencing high flows due to rainfall and/or snowmelt, the plant's efficiency in removing viruses degrades. We have not yet had an opportunity to observe the Portsmouth facility operating under such conditions. Thus, when we see flows at the plant rising due to wet weather or other factors, we will be implementing precautionary shellfish harvest closures that will last a minimum of 7 days. The precautionary closure will allow us to assess any potential issues with virus levels in the effluent."

Nash explained that the precautionary harvest closures would affect Lower Little Bay (Dover Point to Fox Point/Durham Point) and the Bellamy River, and these would occur during the period of October 2020 through March 2021. Upper Little Bay (Fox Point to Adams Point) and Great Bay would not be affected by these precautionary harvest closures. Nash further explained that data from the monitoring efforts this year will be examined to determine the need for precautionary closures next fall and winter.

Changes to the open/closed status of shellfish waters will be announced on the Clam Flat Hotline (1-800-43-CLAMS) and on the NH Coastal Atlas (

For more information on shellfish harvesting in NH, consult the NHDES Shellfish Program website at

NH Department of Environmental Services | 29 Hazen Drive | PO Box 95 | Concord, NH 03302-0095
(603) 271-3503 | TDD Access: Relay NH 1-800-735-2964 | Hours: M-F, 8am-4pm

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