New plan adopted to protect Rhode Island farmed oysters from Vibrio

A new management plan as been adopted by the state of Rhode Island to reduce illness from naturally-occurring bacteria associated with shellfish harvested from aquaculture farms. 

Vibrio parahaemolyticus is a naturally occurring bacterium that is not associated with pollution, but is commonly found in estuaries and coastal marine waters.  There are many varieties of Vibrios and most are harmless to oysters or humans, especially when consumed in small quantities. Unfortunately, Vibrios can multiply rapidly if shellfish are not promptly shaded and chilled following harvest. If shellfish are mishandled and not properly chilled within a few hours the bacteria inside can multiply.

Photo: Rick Friedman

Photo: Rick Friedman

“That’s when it can become a public-health threat,” said Azure Cygler, fisheries extension specialist at Rhode Island Sea Grant and the University of Rhode Island Coastal Resources Center. “It can make people really sick, especially the elderly and those with suppressed immune systems.”

Vibrio illnesses have been linked to wound infections while swimming, as well as consuming undercooked crab, lobster and shrimp as well as shellfish.  While only a handful of shellfish-related illnesses are reported annually in Rhode Island, there has been in increase in illnesses coast-wide in recent years.

“It’s a potential problem that could hurt us in the long run, but we have simple solutions” said Robert Rheault, Executive Director of the East Coast Shellfish Grower’s Association, explaining how a few illnesses can kill a market.


Vibrio Management from Robert Rheault on Vimeo.  Made possible with support from Rhode Island Sea Grant, WHOI Sea Grant, ISSC, NOAA and

In Rhode Island, where oyster farming has grown 30 percent annually for the past decade, shellfish farmers were already being very proactive in icing and chilling their product, according to Rheault.  Despite few cases here, with none reported this year, the increased rate of illnesses in neighboring states has led the FDA to suggest a management plan for Vibrios be developed for Rhode Island.

“The industry proposed a flexible set of state-wide regulations on icing, shade and refrigeration that were far more stringent than those being proposed by the FDA in the hope of protecting their nascent $4.2 million dollar industry, and the hundreds of associated jobs that go with it,” said Rheault, explaining that aquaculture industry leaders met with state regulators to design a set of rules that should minimize risk and ensure that Rhode Island oysters are just as safe on the plate as when they come out of the water.

– The Rules –

From July 1 to September 14, all oysters from enclosed water bodies must be refrigerated or placed in ice within 2 hours.

The new rules affect only oysters and oyster farmers, and require that from July 1 through Sept. 14 all oysters from enclosed water bodies, such as coastal ponds, must be refrigerated or placed in ice within two hours of harvest — (the limit is five hours for oysters from the open bay) — to quickly lower the oyster temperatures below 50 degrees which prevents the proliferation of Vibrios inside the oysters.

All oysters must also be shaded immediately upon harvest, and those oysters that have been removed from the water for husbandry purposes must be re-submerged for two to seven days before being harvested to allow bacteria levels to return to baseline.

The state Division of Agriculture will provide oversight for implementation of the plan, and CRMC will be responsible for monitoring adherence to the new rules. The next step is to develop a similar plan for the quahog industry, which Cygler believes may be more challenging to accomplish due to different harvesting strategies and processing activities. Quahoggers often harvest for long hours each day, she said, and may object to cutting their workday short to deliver their catch to dealers to put on ice. Many also work seven days a week, whereas the dealers they sell to are closed Sundays, so a process will have to be developed for keeping Sunday-caught shellfish cool.

“Illnesses related to clams harvested on Long Island over the past two years should be a motivating factor for our harvesters,” said Rheault

Cygler believes that shellfish dealers, who have not typically participated in the resource management process, may have to become more actively involved, to ensure product delivered to them has satisfied the new Vibrio rules and remains safe for consumers.

A Vibrio control plan for the quahog industry will take effect July 1, 2015. Before this occurs, there will be opportunity for shellfishermen, dealers, and other interested parties to inform the rule-making. Rhode Island Sea Grant, the Coastal Resources Center, and URI will assist in facilitating this process as part of the Rhode Island Shellfish Management Plan effort.

– Meredith Haas | Rhode Island Sea Grant Research Communications Specialist

The Vibrio control plan was facilitated through the R.I. Shellfish Management Plan; a collaboration by the University of Rhode Island’s Graduate School of Oceanography, College of Environmental and Life Sciences, Food Nutrition, as well as Roger Williams University and multiple state agencies, including the Rhode Island Department of Health, Department of Environmental Management (DEM), the Coastal Resources Management Council (CRMC) and the aquaculture industry.

A special thanks to the aquaculture industry and the RI DEM’s Department of Agriculture for their hard work in crafting the Vibrio Plan.