The history and future of the 5% Rule for aquaculture in Rhode Island salt ponds.

The amount of cultured oysters harvested from Rhode Island coastal salt ponds could be increased by 61 times the current production rate without significantly impacting the environment, according to a 2011 study that challenges the current 5 percent of surface area limit for aquaculture development in the salt ponds.

Shellfish aquaculture operation in Potter's Pond, South Kingstown.

Shellfish aquaculture operation in Potter’s Pond, South Kingstown.

However, limiting the area of aquaculture to “5 percent means that 95 percent is available for everything else, and that is unlikely to change,” said David Bengtson, who recently retired from the University of Rhode Island as a professor of fisheries and aquaculture, during a webinar on November 30 sponsored by partners of the Rhode Island Shellfish Management Plan. He explained to participants how the 5 percent rule was established and whether it’s still relevant today. From an ecological standpoint, he said, there is a huge potential to expand aquaculture. That expansion, however, is largely limited by perceived conflicts with other uses of the salt ponds, such as boating, and by the perception that it would mar the area’s general aesthetics.

The Rhode Island Coastal Resources Management Council (CRMC), which is responsible for permitting aquaculture operations in state waters, adopted the 5 percent rule, according to Bengtson, in 2008 in response to stakeholder concerns. Oyster aquaculture in the salt ponds, at the time, was growing faster than in previous years with the total acreage for oyster farms quickly nearing 100 acres and farmers applying for larger leases – which was opposed by many wild harvesters, coastal property owners, and recreational boaters.

The actual percent was loosely calculated based on assessments from Tasman Bay, New Zealand, because “that was the only thing available at the time,” said Bengtson. Tasman Bay was evaluated using an “ecological carrying capacity” approach that accounts for and protects the health of the entire ecosystem, as opposed to assessing how much can be produced in a given area. This is an important distinction, because the latter approach “only looks at the upper limit of what is allowed, and it’s not recommended,” he said, referring to an industrial operation in China where the natural system had been disrupted, making production unsustainable. “We don’t want to be like that.”

Shellfishermen harvesting in Ninigret Pond.

But there are obvious caveats to the more holistic Tasman Bay approach that Bengtson pointed out. Tasman Bay itself is the about size of Rhode Island and has a more oceanic environment with likely less primary production from phytoplankton than the coastal salt ponds. In addition, the Tasman Bay assessment looked at mussels, not oysters, which make up the majority of aquaculture in Rhode Island.

Given the lack of resources, however, the biological subcommittee for CRMC’s Working Group on Aquaculture Regulations, a stakeholder group that Bengtson chaired, used Tasman Bay numbers to roughly calculate and recommend a 5 percent limit for oyster aquaculture in Rhode Island’s coastal salt ponds. The group also recommend further research to calculate the actual ecological carrying capacity of the ponds, and Narragansett Bay, given the limits of the Tasman Bay study.

According to Tasman Bay calculations, about 65 tons per square kilometer could be harvested annually without significantly impacting the food web. By applying that assumption to the total area of Point Judith Pond, one of the largest coastal ponds at 6.37 square kilometers, it was estimated that 414 tons could be harvested within the ecological carrying capacity parameters. At the time, said Bengtson, stock density was estimated at 5 tons per acre, meaning that roughly 83 acres could be devoted to aquaculture – or 5 percent of the total area. This calculation for Point Judith Pond was applied to all of the salt ponds as a way to regulate aquaculture development.

“There was only 2.4 percent coverage of oyster culture within the ponds at the time. So as the various stakeholders discussed this, those in the aquaculture industry recognized there was still plenty of room to grow, and those less enthusiastic about aquaculture felt that 5 percent wasn’t that much. It became a de facto agreed-upon standard,” he said.

“No pond has hit 5 percent to date,” said Dave Beutel, CRMC aquaculture coordinator during an aquaculture tour in early September of Ninigret Pond, one of the largest of Rhode Island’s coastal salt ponds located in Charlestown. “Ninigret is currently at 2.8 percent, pending applications that would take it to 4 percent.”

Like Point Judith Pond, Ninigret Pond is one of the most heavily used coastal salt ponds in Rhode Island that supports aquaculture. The majority of operations focus on oysters, although some interest exists in growing mussels, clams, scallops, and kelp. The industry is expected to continue growing, as the market value of these products has increased twenty-fold in the past two decades to about $6 million, with the number of farms steadily increasing every year. Currently, there are 61 farms operating in Rhode Island, cultivating over 240 acres, in addition to several pending applications, according to CRMC’s 2015 report.

While the ecological carrying capacity study Bengtson cited indicates substantial room for growth of aquaculture without significantly impacting the environment, the social carrying capacity – what the public finds acceptable – is another matter.

“It’s no longer an ecological issue but a social one,” he said.

Rhode Island Sea Grant is funding Tracey Dalton, a social scientist and URI professor of marine affairs, to examine public opinions of aquaculture, as well as current and projected public uses of potential aquaculture sites (“Perceptions of Aquaculture”).

“We’re trying to understand where do people agree or disagree on certain levels of aquaculture … whether the commercial harvesters think differently than the aquaculture farmers or the general population in terms of how much aquaculture is acceptable. And we are finding some differences,” said Dalton during a presentation last April for Rhode Island Sea Grant’s Coastal State Discussion Series.

Although her initial findings through a small sample survey showed that a high percentage of coastal property owners believe that the presence of shellfish farms spoils the beauty of the ponds and inhibits navigation for boaters (Read more from ecoRI), Dalton is still collecting and assessing survey data. A final report will be available in the spring of 2017 that will help inform state management efforts.

Additional research underway by Robinson Fulweiler from Boston University is investigating the role oyster farms may play in removing excess nutrients and promoting a healthier ecosystem (“Oyster Aquaculture & Water Quality”). Her research is intended to help oyster growers determine how to best configure their farms for optimal nitrogen removal, which also means fastest oyster growth, as well as provide information to help enhance aquaculture operations, as a whole, for improving water quality in Narragansett Bay and the coastal salt ponds.

If you missed the webinar, it is available online. 

[info]The 5% Rule webinar was hosted by partners of the Rhode Island Shellfish Management Plan: the Coastal Resources Center and Rhode Island Sea Grant at the University of Rhode Island Graduate School of Oceanography, through a partnership grant from NOAA’s National Sea Grant office, in collaboration with CRMC and Roger Williams University. For more information and updates on future events, please visit[/info]
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2016 spring Coastal State Discussion Series: Dr. Tracey Dalton, and graduate student
Emily Patrolia, discuss perceptions of aquaculture and impacts of climate change on
recreation in Rhode Island’s coastal salt ponds.

Aquaculture and Recreation Vie for Salt Pond Use

Ninigret Aquaculture Tour

Raising Objections: Hurdles for Rhode Island Aquaculture


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Meredith Haas | Rhode Island Sea Grant Communications

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