Shellfishing FAQs

American oysters and blue mussels are the most common types of shellfish farmed commercially in the state. Some limited culture of other species such as softshell clams, razor clams, scallops, and hard clams occurs as well.  

Natural populations of softshell (steamer) clams and oysters are not harvested commercially. Those natural stocks are reserved for recreational harvest only. The NH Fish and Game Department allows limited commercial harvest of some species, such as scallops and surf clams. 

The NH Fish and Game Department regulates aquaculture operations, and evaluates applications for aquaculture licenses. The evaluation process involves a site assessment for purposes of verifying or updating information included in the application, consults with the NH Department of Environmental Services for water quality information, conducts a public hearing for public input of the proposed site, and assures state and federal regulators and abutting landowners are notified of the application (Fis807.07). Farms are not allowed on areas with natural shellfish populations, eelgrass beds, or other ecologically important characteristics. The NH Fish and Game Department then reviews all of the information to determine that the proposed aquaculture operation will not pose any unacceptable risk, does not conflict with or negatively impact any recreational, commercial or other use currently being conducted in the area in and around the projected area before issuing a license. 

Red Tide monitoring in New Hampshire has two components: weekly testing of blue mussel tissue for PSP toxin from two locations, and weekly examination of seawater samples to detect the presence of harmful algae bloom species. 

The monitoring program has typically consisted of at least weekly collection and testing of blue mussels, which tend to accumulate the PSP toxin quicker than other species of shellfish, from Hampton/Seabrook Harbor. The weekly testing is performed on samples of mussels from April through the end of October, the period when the phytoplankton may be active. Conditions in offshore waters, where PSP blooms tend to originate, are tracked by weekly sampling of blue mussels from Gosport Harbor, Isles of Shoals.  Data-sharing with neighboring states of Maine and Massachusetts has been an integral part of ensuring an adequate, large-scale monitoring program across the Gulf of Maine.

PSP is not the only type of harmful algal blooms that can affect shellfish consumers in the Gulf of Maine.  For the period of February through November, the NHDES Shellfish Program collects weekly samples of seawater from two offshore sites and three nearshore sites, and identifies the numbers and types of algae cells under a light microscope.  When harmful species are identified in numbers that suggest a possible public health issue, the sample is screened for the presence of toxins, and additional tests on shellfish tissues are performed as needed.

NH shellfish waters are closed for harvesting when the PSP toxin levels in blue mussels reach 80 micrograms of poison per 100 grams of mussel tissue. However, PSP toxin levels can change very rapidly over the course of just a few days. Therefore, waters may be closed for lower amounts of toxin, especially when NH stations are showing rising levels of toxin, and nearby stations in southern Maine or northern Massachusetts are showing levels higher than the 80 microgram limit. 

PSP harvest closures in the Hampton/Seabrook Estuary are listed below.  2005, 2008, 2014, and 2019 are among the years with the greatest number of samples with high toxin measurements in blue mussel tissue. 

*harvest closure listed as ending May 31, as the area went into regular seasonal closed status after that date.  High toxin levels may have occurred after that date. 

**samples with high toxin levels were collected AFTER the regular seasonal closure went into effect. 

Commercial Shellfish Farming, or “Aquaculture'' means the propagation and rearing of aquatic species and marine species and includes the planting, promoting of growth, harvesting and transporting of these species in, on, or from the waters of this state (RSA 211:62-e) 

Shellfish beds remain closed until there has been adequate flushing of pollutants from the affected waterbody, and the shellfish have had adequate time to purge themselves of contaminants. The amount of time that shellfish beds will remain closed is 14 days after the rainfall event, or sooner if water and shellfish tissue samples show that harvesting conditions are once again safe. In recreationally-important areas such as Hampton/Seabrook, NHDES usually conducts water and meat sampling to determine if the closure can be lifted sooner than the typical 14-day period.  Often closures are lifted before the 14-day period elapses.

Microscopic algae are single-celled plants that live in the sea. Most species of algae or phytoplankton are beneficial to the ecology of the ocean, serving as the base of the food chain, which supports higher forms of life such as fish, birds, marine mammals, and humans. 
Occasionally, the algae grow very fast or "bloom" and accumulate into dense, visible patches near the surface of the water. Some species of phytoplankton contain reddish pigments, and an intense bloom of these species can make the water appear to be colored red. The term "Red Tide" is a common name for such a phenomenon, although the term is really a misnomer because such events are not associated with tides. Many of the phytoplankton that can discolor the water are not harmful, and those species that are harmful may never reach the densities required to discolor the water. 
Although most phytoplankton species are not harmful, a small number of species produce potent neurotoxins. The toxins can be transferred through the food chain, where they affect and even kill the higher forms of life such as zooplankton, shellfish, fish, birds, marine mammals, and even humans that feed either directly or indirectly on them.

Although there are several species of phytoplankton that can cause a variety of illnesses, the main illness of concern in NH waters is Paralytic Shellfish Poisoning, or PSP. Various species of the phytoplankton Alexandrium are the chief causative agents of PSP. Alexandrium cysts spend the winter in offshore ocean sediments in a dormant state. In response to increased sunlight and temperature in the spring, the cysts germinate into free-swimming cells, which reproduce by cell division. If water conditions are good, the cells continue to divide, and growth is exponential - a single cell can result in the reproduction of several hundred cells in just a few weeks. If other single cells are reproducing in a similar manner, this large "bloom" can result in shellfish toxicity.

Paralytic Shellfish Poisoning, or PSP, is a life-threatening syndrome, and the onset of symptoms is rapid, usually within two hours of consumption. Symptoms include tingling, burning, numbness, drowsiness, incoherent speech, and respiratory paralysis. Duration of effects is a few days in non-lethal cases. The most severe cases result in respiratory arrest within 24 hours of consumption of the toxic shellfish. If the patient is not breathing or if a pulse is not detected, artificial respiration and CPR may be needed as first aid. Although there is no antidote, supportive therapy and treatment is usually adequate, and survivors recover fully. PSP is prevented by large-scale proactive monitoring programs (assessing toxin levels in filter feeding mollusks such as mussels, oysters, clams, and/or scallops) and rapid closures to harvest of suspect or demonstrated toxic areas.

A snow storm (without any form of rain) does not warrant a closure, because such storms do not produce significant runoff. A closure may be instituted if a snow storm occurs with rain, or the snow accumulation quickly melts and causes polluted runoff.

Yes. All commercial shellfish farms are required to mark the boundaries of their site with yellow buoys with reflective tape. Farmers are typically given the option of removing buoys for the winter to avoid ice damage.

Shellfish farming does not involve the introduction of artificial food supplies, a practice that is necessary for other types of aquaculture such as finfish farming. Shellfish growing on aquaculture farms filter-feed natural populations of microscopic plants and animals from the natural habitat.

Yes.  In New Hampshire, commercial aquaculture occurs in tidal waters, which are open to the public. An aquaculture license grants the licensee permission to use those public lands, but the licensee does not have exclusive rights to the area. Members of the public may still boat, fish, or recreate on those waters. Boaters should understand, however, that some aquaculture sites may have a lot of cages, lines, and other gear, which can foul and/or damage boats and boat engines. Members of the public should remember that it is unlawful to disturb, molest, tend or possess any aquaculture gear OR the marine species being raised in a licensed marine aquaculture area without written permission of the licensee. 

Modern shellfish aquaculture is subject to a number of regulatory and oversight measures designed to minimize health risks from commercial shellfish farms. Farms are only located in waters approved by the NH Department of Environmental Services, using testing procedures and evaluation protocols that are uniform across the nation, and evaluated the U.S. Food and Drug Administration.  These waters are routinely monitored by NHDES for public health issues such as high bacteria levels, the presence of “red tide” toxins, etc. Additional, more intensive testing is performed by NHDES when conditions dictate such measures.  All shellfish farmers are required to check with NHDES before every harvest to confirm there are water quality issues at their site.  Furthermore, the Department of Health and Human Services ensures commercial farmers and their staff are knowledgeable in safe food handling practices, performs unannounced inspections each year, and requires additional safety measures such as time/temperature controls during warm weather months.

Modern shellfish aquaculture in New Hampshire does not involve the introduction of chemicals, pesticides, antibiotics, or other harmful substances.  The growth of large numbers of filter-feeding shellfish is generally regarded as positive for water quality and the environment. These filter feeders trap particles of food as well as nutrients and suspended sediments, thereby helping keep the water clean and clear for underwater grasses and further supporting the marine ecosystem. Farmed oysters typically release large numbers of oyster larvae into the adjacent waters each summer, introducing even more filter-feeding shellfish to the environment.  Aquaculture gear and cages are typically colonized by a number of plants and animals that use it as habitat. 

Week-to-week decisions on the open/closed status of areas such as the Hampton/Seabrook Estuary are largely driven by weather conditions. In rainy seasons such as spring and fall, weather forecasts often change from day to day, and whenever possible, NHDES strives to make decisions based on actual weather conditions, rather than forecasts. Thus, it is necessary to delay announcing open/closed decisions until the latter part of the week. 

Another reason that updates are made later in the week is related to sampling activities. Rather than always relying on automatic closures of the harbor when rainfall exceeds certain levels, NHDES collects water and shellfish tissue samples following some rainfall events for the express purpose of making weekly open/closed decisions – if samples show low bacteria levels, the harbor is opened for harvesting, regardless of how much rain fell. Laboratory test results on water samples collected on Mondays or Tuesdays are often not available until Wednesday or Thursday; thus, the announcement of the open/closed status for a particular week is sometimes delayed until later in the week.  

The NH Clam Flat Hotline at 1-800-43-CLAMS and the NH Coastal Atlas are always updated on Fridays. Some recreational harvest areas (e.g. Little Bay and Bellamy River) are open only on Saturdays, starting at 9:00 am. Harvesters are encouraged to check the NH Clam Flat Hotline at 1-800-43-CLAMS and/or the NH Coastal Atlas Saturday mornings to make sure their area of interest is open for harvest. Saturday morning updates, when necessary, are done by 8:30 am on Saturday. 

In Great Bay, shellfish beds at Adams Point are accessible by foot, while the resources around Nannie Island are accessible by boat. Hampton/Seabrook Harbor shellfish beds are accessible by both foot and boat. Motor vehicles are prohibited on any tidal area, exposed at low tide, which is capable of growing clams. Use the NH Coastal Atlas to find coastal access points, coastal public beaches and shellfish harvest areas. 

The New Hampshire Department of Environmental Services (NHDES) is responsible for determining which of the state’s tidal waters are appropriate for shellfish harvest and consumption. NHDES: 

• identifies and tracks pollution sources, monitors seawater 

• regularly checks seawater and shellfish for possible contamination of sewage 

• monitors for the presence of naturally occurring toxic algae blooms, commonly known as “Red Tide” 

• monitors weather conditions and implements temporary harvest closures as needed 

• interfaces with commercial shellfish farmers to prevent harvest of shellfish during periods when there may be contamination 

• maintains open communications with local wastewater treatment facilities and municipal Department of Public Works staff to stay informed about any accidental sewage discharges 

The New Hampshire Fish and Game Department is responsible for enforcing the "open/closed" status of shellfish growing waters. Fish and Game also controls harvesting through license sales and other means, evaluates and manages the health of the shellfish resources, and issues licenses for shellfish aquaculture projects, or other commercial harvesting operations. 
The New Hampshire Department of Health and Human Services is responsible for the laboratory analysis of water samples and shellfish tissues. DHHS also certifies and inspects commercial shellfish operations such as dealers, shucker/packers, and aquaculture ventures. 

NHDES works closely not only with F&G and DHHS, but also with a number of other organizations including the U.S. Food and Drug Administration, staff from all of the NH Seacoast cities and towns, the Interstate Shellfish Sanitation Conference,  NH Coastal Program, the Woods Hole Oceanographic Institution, the Bigelow Laboratory for Ocean Sciences, the Piscataqua Region Estuaries Partnership, the University of New Hampshire/Jackson Estuarine Laboratory, and the US Environmental Protection Agency,. NHDES has also formed partnerships with the private sector, including NextEra Energy Seabrook Station, Great Bay Marine, Inc., and the Star Island Corporation. 

The New Hampshire Fish and Game Department does not currently seed the clam flats or oyster beds.

Shellfish harvested from "closed" areas have the potential to result in illness if they are consumed, because filter-feeding shellfish can concentrate harmful bacteria and viruses. When contaminated shellfish are eaten by humans, serious illnesses such as gastroenteritis, septicemia, hepatitis, cholera, and typhoid can result. These illnesses occur mainly from the result of human sewage, as well as animal wastes, reaching the shellfish growing waters. 

Sometimes harvesting is closed because of harmful algae blooms, such as those responsible for Paralytic Shellfish Poisoning (PSP).  PSP or "Red Tide" is caused by a population "bloom" of naturally occurring, microscopic algae which produce a potent neurotoxin. These toxins can accumulate in the bodies of filter feeding bivalves, such as clams, mussels and oysters which ingest the organisms. Humans who eat the shellfish may become afflicted with PSP. PSP may cause death through respiratory paralysis. Less severe symptoms start with numbness in extremities and/or tingling of the lips. Although PSP is the most common type of harmful algal bloom to affect NH shellfish, there are other harmful algal blooms which can cause memory loss, gastrointestinal problems, or other symptoms in those who consume the contaminated shellfish.  NHDES examines seawater samples every week, February through November, from several nearshore and offshore locations to check for the presence of harmful algal blooms.  Results from these weekly tests determine if shellfish tissues need to be tested for the presence of toxins. 

During the warmer months, those who harvest and eat raw shellfish such as oysters need to take special precautions.  Naturally occurring species of Vibrio bacteria can cause gastrointestinal illness, especially if shellfish are not kept cool.  Recreational and commercial shellfish harvesters should always make sure that harvested shellfish are immediately cooled, and kept cool, to minimize risk of illness. 

The consumption of raw shellfish, even if harvested from open areas, can carry an inherent health risk. This is especially true for people who suffer from liver disease, weakened immune systems, or other health problems. Such people are at greater risk not only from the illnesses associated with human or animal waste, but also from illnesses caused by naturally occurring bacteria. 

Adequate cooking of shellfish will destroy harmful bacteria and viruses, thereby eliminating the health risks associated with them. The Interstate Shellfish Sanitation Conference recommends the following guidelines to ensure adequate cooking of shellfish:  

• Tips for Cooking Oysters & Clams in the Shell  

• Boil live oysters in boiling water for 3 to 5 minutes after shells open, or steam 4-9 minutes. Use small pots to boil or steam shellfish. Do not cook too many shellfish in the same pot because the ones in the middle may not get fully cooked. Discard any shellfish that do not open during cooking. 

• Steam live oysters 4 to 9 minutes in a steamer that is already steaming. 

• Cook to an internal temperature of 140oF or more for 4-6 minutes. 

• Tips for Cooking Shucked Oysters & Clams  

• Boil or simmer for at least 3 minutes or until edge curl. 

• Fry in oil for at least 3 minutes at 375° F. 

• Broil 3 inches from heat for 3 minutes. 

• Bake for 10 minutes at 450° F. 

Although adequate cooking will kill bacteria and viruses, it does not eliminate the danger of eating shellfish contaminated by "Red Tide”. Paralytic Shellfish Poisoning is a condition caused by a toxin, not by a bacteria or virus. The heat from cooking will not destroy the toxin. 

Waters documented as polluted through the sanitary survey are permanently closed to harvesting. Many other areas in coastal New Hampshire are "conditionally approved," meaning water quality is good under certain conditions, but poor under other conditions. Such areas are often subject to temporary harvest closures, typically following heavy rainstorms or during certain seasons such as summer.  During these temporary closures, high bacteria levels in the shellfish growing waters indicate the presence of human or animal waste, and shellfish exposed to this contaminated water can cause illness if consumed by people. Sources of bacteria include malfunctioning, improperly installed, or poorly maintained septic systems, municipal and industrial discharges of wastewater, illegal sewage discharge from boats, waterfowl and wildlife wastes, and polluted stormwater runoff. 

Rainfall can cause temporary shellfish bed closures because rainwater runoff often transports high levels of pollution into the shellfish growing waters. Some waterbodies can only assimilate small amounts of rainfall/runoff before they become polluted, while other waterbodies can handle larger rainfall events and still be safe for shellfish harvesting. 
Shellfish beds are closed when they are subject to accidental releases of untreated sewage or hazardous materials such as petroleum products. 

Beds in close proximity to wastewater treatment plant outfalls and marinas are permanently closed. 
Areas where no sanitary survey has been conducted are closed as a safety precaution. These waters are designated as "unclassified." Additionally, if the sanitary survey is not kept current through mandatory three-year updates, the area must be closed. 
Incidences of "Red Tide," which can cause Paralytic Shellfish Poisoning, will also cause closures. Red tide is caused by "blooms" of microscopic algae which produce a potent neurotoxin. When these algae populations reach high densities, the toxin can be concentrated in shellfish, which in turn pose a potential health risk to shellfish consumers. Once levels of toxin in shellfish reach an established threshold, shellfish harvesting is stopped in affected areas. 

Some shellfish beds are closed for resource conservation for some or all of the summer. 

Rains can cause temporary shellfish bed closures because stormwater runoff is known to transport pollution into surface waters. Pollutants come from feces (humans, animals, and birds), boats and marinas, industrial and farm use (e.g., pesticides, plastics, detergents, oil, and gasoline), industrial effluents and surface runoff (e.g., acids, caustics, salts, and metals), and road and highway runoff. Some shellfish beds will be closed after a rainfall event until adequate flushing of the shellfish growing areas has occurred and the shellfish themselves have had a chance to purge themselves of pathogens.

Open and Conditionally Open areas are depicted in the NH Coastal Atlas maps. Some areas are only open when specific weather conditions are met – visit NH Coastal Atlas or call the NH Clam Hotline at 1-800-43-CLAMS for regular updates. Additional information can be accessed through the NH Fish and Game Department Web site.

By regulation, a public hearing is always part of the evaluation process. These hearings provide the opportunity for the applicant to present details of the proposed aquaculture sites and operation to the public and address questions and concerns regarding potential conflicts with existing uses of the area being considered. Abutting property owners are informed about the application and the scheduled public hearing directly. Non-abutting property owners, as well as other members of the public who may have concerns about the project’s location or other details, are invited to attend the public hearing as well. Public hearing announcements can be found on the NH Fish and Game website.

The major softshell clam flats are located in Hampton Harbor, with scattered beds in the Great Bay Estuary. Surf clams and mahogany quahogs are found along the Atlantic Coast. The major oyster beds, as well as scattered populations of razor clams, are found in Great Bay and other areas. Blue mussels can be found in Hampton Harbor and in rocky areas along the coast. For more detailed information, contact the New Hampshire Fish and Game Department. 

Recreational harvest of softshell clams and/or oysters, both require a NH Fish and Game license. Buy a NH Recreational Softshell Clam or Oyster License. 

Recreational mussel, surf clam, razor clam, and mahogany quahog harvesting do not require a license. Download the NH Saltwater Digest Harvest Regulations. 

Yes.  In New Hampshire, all aquaculture license holders pay an annual fee for their license, as well as fees based on how many acres of public land they are using. In addition, oyster farmers pay a fee of $0.015 for each oyster harvested. These fees are paid to the NH Fish and Game Department to help cover the cost of site evaluation, annual inspections, and enforcement.