Research 2014–2016

Research Projects 2014–2016

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Alan Desbonnet
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Rhode Island Sea Grant is placing research emphasis in the areas of shellfish biology, the ecology of the resources that support shellfish, and shellfish management. This emphasis was chosen based upon requests from resource managers, permitting agencies, commercial and recreational shellfish harvesters, and shellfish aquaculture business owners for new knowledge and improved understanding of shellfish and shellfish resources.

Outcomes of Sea Grant-funded research will be used in support of an initiative undertaken by the R.I. Coastal Resources Management Council and the R.I. Department of Environmental Management, in partnership with Sea Grant and other entities, to develop the Rhode Island Shellfish Management Plan. Our understanding of the important role that shellfish play in the economy and ecology of Rhode Island will also be enhanced by outcomes of this research agenda.



Whelks are large marine snails that are rapidly becoming a market commodity in both the U.S. and Asia.

Understanding Whelk Biology in Response to Overfishing in Rhode Island

Whelk has largely been an unregulated fishery in Rhode Island until recently as concern has risen due to perceived overfishing.

Managers currently lack basic knowledge about the life cycle of whelk needed for adequate management decisions – especially concerning size limit, which is currently based on consumer demand rather than biological attributes.

Rhode Island Sea Grant funded University of Rhode Island researcher Kathleen Castro to investigate local and scientific knowledge on the biology, ecology, and fishery for whelk in Rhode Island waters to help resource managers and fishermen develop better harvesting practices.

Researchers found that in the field knobbed whelk were avid predators of hard clams especially in the warmer months; channeled whelk less so. Both species will choose other prey items, such as mussels, when available.

Results suggest that predator-prey interactions should be included as an ecosystem-based approach to managing the shellfish stocks in Narragansett Bay. In addition, the long maturity duration for both species (8+ years) is linked to stock depletion due to overfishing practices on animals before they reach reproduction age.

Female channeled whelk had the highest mean annual growth rates (15.70 mm shell length, 9.21 mm shell width, and 7.13 mm shell height) – reaching minimum legal size fastest on average at 8.4 years. Male channeled whelk followed (14.32 mm SL, 8.21 mm SW, 6.35 mm SH) reaching legal harvest size around 9.36 years; female knobbed whelk (14.26 mm SL, 7.87 mm SW, 5.98 mm SH) at 9.69 years; and male knobbed whelk (12.98 mm SL, 7.02 mm SW, 5.26 mm SH) at 10.85 years.

These results will be used to help the R.I. Department of Environmental Management manage the species on an ecologically and economically sustainable basis, and to inform whelk management initiatives now being formulated by the Atlantic States Marine Fisheries Commission.


Matunuck Oyster Farm

Matunuck Oyster Farm

Oyster Aquaculture Helps Remove Nitrogen

Shellfish aquaculture is a rapidly growing business in Rhode Island with little known about the impacts to the environment over time, and whether shellfish, such as oysters, are a potential solution for reducing excess nutrients (nitrogen) that can cause harmful algal blooms, reduce oxygen availability in the water column, and contribute to fish kills.

Rhode Island Sea Grant funded researcher Robinson Fulweiler from Boston University, in collaboration with several Rhode Island oyster growers, to investigate how nitrogen cycling processes, in general, and nitrogen removal processes vary over time in rack and bag oyster aquaculture in southern Rhode Island.

“I’m interested in what oysters do to nitrogen,” said Fulweiler. “They indirectly remove nitrogen by filtering carbon out of the water, depositing feces on the bottom, which fuel bacterial processes that remove nitrogen. On the flip side, if oysters aren’t being taken care of you can get the opposite process and actually add nitrogen to the system.”

Her research will help oyster growers determine how to best configure their farms for optimal nitrogen removal, which also means fastest oyster growth. Fulweiler’s research will help Rhode Island’s growing aquaculture industry improve performance in providing the additional service—above and beyond that of providing jobs and fresh seafood—of improving water quality in Narragansett Bay and the south shore coastal lagoons.

“My goal is to make this data available as fast as we can to the shellfish aquaculturists,” she said, noting that the shellfishermen have been extremely helpful in collecting information. “They work on the ponds every day and know the systems better than we can.”

Fulweiler identified test sites on aquaculture farms ranging in age from 0-3 years, 3-5 years, and greater than five years to determine the duration each rack and bag setup should remain in one place to maximize nitrogen removal processes to improve water quality.

The first sampling collected data on summer oxygen demands, nutrient fluxes, and nitrogen fluctuations from core samples, as well as samples from the water column to characterize sites based on dissolved oxygen, salinity, and chlorophyll levels.

Preliminary results show that sediment beneath oyster aquaculture serves as a sink for nitrous oxide (N2O), and rates of sediment N2O uptake do not vary with the length of time aquaculture gear has been in place – suggesting that oyster aquaculture removes nitrogen at an enhanced rate compared to control sites, but does not alter greenhouse gas fluxes.

The final analysis is underway.


Clamininbag2Warming Waters Important for Quahog Larvae and Retention in Narragansett Bay

Rhode Island’s quahog harvest industry, estimated at $5 million, has been managed by reducing harvest limits in alleged spawning sanctuaries. In addition, the recent activation of the Combined Sewer Overflow treatment facility in upper Narragansett Bay is anticipated to improve water quality, potentially opening previously closed waters for harvesting that may be critical larval sources for Narragansett Bay.

Rhode Island Sea Grant researcher Scott Rutherford at Roger Williams University, in collaboration with Chris Kincaid and Dave Ullman from the URI Graduate School of Oceanography, to investigate the dispersion of quahog larvae in Narragansett Bay and compare to adult densities, as well as how dispersion may be impacted by various climate factors, such as warming waters, with the goal to help managers determine areas for habitat restoration or other management strategies.

Researchers found that the larval source to the main quahog harvest grounds is dominated by closed or conditionally closed waters, not designated spawning sanctuaries, and that warmer water leads to more quahog larvae being retained in Narragansett Bay – though it is speculated that larval development stages may be shortened by one day assuming modest warming by 2060. How warming waters may change larval distribution and adult densities is still unknown.

They also found changes in larval density patterns that may alter fishing grounds and management needs.

Drifter to measure surface current flow direction.

Drifter to measure surface current flow direction.

To determine larval distribution, Rutherford and his team developed drifters to mimic the behavior of floating quahog larvae to get an idea of where they might end up based on the direction of the currents. Over 30 drifters, both at 1 meter and 3 meters in length, were deployed from Ohio Ledge to see how different layers of the water column impact dispersal. All of the drifters were shown to end up somewhere in the East Passage of the Bay, which is contrary to general thinking that Bay circulation flows counter-clockwise. In general, it was found 1 meter drift traveled into both the East and West Passages, whereas the 3m drifters preferred the East Passage.

All of the drifters were shown to end up somewhere in the East Passage of the Bay, which is contrary to general thinking that Bay circulation flows counter-clockwise. In general, it was found 1 meter drift traveled into both the East and West Passages, whereas the 3m drifters preferred the East Passage.

The depth of the stratification, however, was different in the two passages, being deeper in the East Passage. This allows for both 1m and 3m drifters to exit to the east in southward surface flow but inhibits southward transport to the west of the 3m drifters, where the flow is dominantly northward. Overall, the drifter/model comparisons are demonstrating a flow structure that is highly variable laterally, vertically, and temporally.

Model simulations of climate change scenarios are ongoing along with weighting larval releases by fecundity and adult density to provide better quantitative estimates of larval source/sink relationships.

Parasites Linked to Blue Mussel Depletion in Rhode Island

Blue mussels are an important food product supplied from both wild harvest and aquaculture efforts. However, newly recruited Narragansett Bay mussels are being used to seed existing and proposed mussel culture sites without understanding the risk of transporting significant pathogens. These diseases have the potential to significantly adversely affect mussel aquaculture as well as the wild fisheries, both ecologically and economically.

Roxanna Smolowitz, a researcher from Roger Williams University, received Sea Grant funding to investigate blue mussel pathogens common to Narragansett Bay in order to minimize aquaculture-based disease outbreaks. Results are intended help prospective mussel growers design and implement husbandry practices that will minimize the on-farm disease outbreaks.

Smolowitz and her team collected blue mussels of three sizes (15 to 30 mm, 30-45 mm, and >45 mm) from Arnold Point, Hope Island, Roger Williams University Dock, East Passage, and West Passage to compare wild harvests to cultured animals.
Various diseases, especially those caused by digenetic trematodal and microsporidial infections, have been identified in mussel populations in Rhode Island and the northeast.
Findings suggest a strong relationship between the parasitic trematode Parahaemolyticus Maculates and blue mussels that correlated with observed temperature and annual mortality increases, including observed low reproductive rates of mussels. Results also demonstrate the need for uninfected mussel seed in aquaculture practices and highlighted future research needs in determining the transference of the parasite between mussels and fish, potentially altering timing of harvests, as well as how temperature affects the life cycle of these parasites to help aquaculturists and regulators to better understand infection and develop management alternative management methods.

Aquaculture in Ninigret Pond

Social Carrying Capacity Baseline Developed for Aquaculture Growth in Rhode Island Coastal Salt Ponds

Over the past twenty years, the amount of submerged land used for aquaculture in Rhode Island has been growing steadily with some stakeholders expressing concerns about user conflicts, leaving coastal managers in need of more knowledge concerning the social issues related to aquaculture development.

Tracey Dalton and Robert Thompson from the University of Rhode Island, in collaboration with Di Jin from the Marine Policy Center at the Woods Hole Oceanographic Institution, investigated the perceptions of aquaculture in Rhode Island’s salt ponds, which are the focus of a growing aquaculture industry, to determine various factors that influence support or opposition to aquaculture in order to minimize conflict where possible and provide suggestions to current aquaculture practices that could lead towards improved support.

In July and August 2014 Dalton and her team have worked on developing a mail survey that focuses on various types of aquaculture and locations.Two different sites, one in the bay and one in a coastal pond, are being used in photo simulations for the survey to depict farm size and operations.

“Our plan is to develop a survey of Rhode Island residents, targeting commercial harvesters, aquaculture farmers, waterfront property owners, and then a general sample of coastal residents to understand their level of support,” said Dalton, explaining that answers to the survey questions can help them understand whether certain characteristics of people correlate with opposing aquaculture in all forms or support.“Aquaculture can look different in different places, and people have different attachments to different places, which is why we’re focusing on two different places,” she said.

Based on these surveys and interviews, Dalton and her team found that levels of social acceptability for aquaculture declined with increasing aquaculture activity and that those without a water view had higher acceptance levels than those with a water view, or who was a wild harvester or a retired individual.

The level of support was positively associated with attitudes related to shellfish aquaculture’s benefits to the local economy and its role as a nutritional food option, and negatively influenced by attitudes related to aquaculture farms’ effects on aesthetic quality and their interference with other uses. Findings highlight that support for (or opposition to) aquaculture in Rhode Island is driven more by attitudes associated with social impacts than by those associated with environmental impacts. The level of support is also affected by personal characteristics related to an individual’s participation in recreational activities.

Results have helped establish a dialogue between social scientists, stakeholders, and coastal managers to help determine future aquaculture development. 


Rhode Island’s coastal ponds are highly valued for a range of recreational and commercial activities but have a limited capacity. How people use the coastal ponds, why, and with what intensity will help resource managers develop plans to minimize conflict and preserve, or enhance, assets users value most.“I can tell you there are a lot of people there and what they’re do, generally, but I can’t tell you why they’re doing it there, and what they think about it,” said Robert Thompson, a researcher at the University of Rhode Island.Robert Thompson, Tracey Dalton and James Opaluch of URI, in collaboration with John Lake and Eric Schneider of the R.I. Department of Environmental Management Division of Fish and Wildlife, will inventory and map coastal resources and their recreational and commercial uses along Rhode Island’s south shore. They will improve this inventory with information about how users value the resource, for instance for boating and shellfishing.“We’re trying to collect high-resolution spatial data of human uses of coastal ponds that can be built into models of ecosystem services,” he said, explaining that people respond to fish activity and other biological factors. We’re trying to include people as part of the ecosystem.”This information will assist resource managers in developing plans of use that avoid, or at least minimize, conflicting uses, and that will help develop management strategies that preserve and enhance those assets that users value highest.

Binoculars with laser locators were used to identify GPS points of various activities in the coastal ponds.

Binoculars with laser locators were used to identify GPS points of various activities in the coastal ponds.

Thompson and his team completed 30 observational days on Point Judith Pond, Potter Pond, Ninigret Pond and Quonochontaug Pond to observe daily activities.Multiple surveys, which include observational and in-person interviews, have been developed to compare human activities and biological abundance in ponds. Many activities overlap but are not generally in conflict with each other.“The misconception is that people view overlapping uses as in conflict,” said Dalton, noting that’s not always the case. Part of the survey, she said, focuses on what people think about other uses around them, and targets specific areas of use to evaluate areas that are more highly impacted by humans.“Not everyone is using the same space at the same time,” said Thompson.The team will process information this winter of 2015, and will continue surveys in the spring and summer of 2015 to increase the database and correct any gaps.“There are a lot of activities originating from private marinas and beaches that we’re not intercepting, and we need to access them and learn what they think,” said Thompson.This project will incorporate findings from Dalton’s work on the perceptions of aquaculture to help manage potential conflicts as operations expand, and will also look at the recreational value of different sites based on travel costs.



What impacts do aquaculture operations have on Rhode Island’s salt ponds?

URI researcher, Mark Stolt, will be evaluating whether oyster aquaculture benefits ecosystem functioning in southern Rhode Island’s coastal salt ponds – specifically, Ninigret, Winnapaug, and Potter Pond.These submerged ponds represent areas with and without aquaculture, and will be compared based on submerged soil types, water quality, and aquatic organisms to decipher environmental impacts of aquaculture.“We’re trying to get a picture of what’s happening to these soils as a reflection of the aquaculture that’s going on,” said Stolt, explaining that the condition of the soils are indicative of the water quality, the tidal fluctuation, and how much energy (food) is coming in.This research will provide information for specific regulatory decisions in regards to shellfish aquaculture, and the capacity of the environment to sustain increased production.

Stolt is evaluating several aquaculture sites of different ages from 3 to 17 years to better understand the interaction between bivalve growth and soil condition over time, which will reflect the health of the environment. He will also be evaluating the benthic communities on the same soil type in areas where there is no aquaculture.“We’ve identified our sites, and have just started sampling for benthic organisms to characterize the soils under different age [aquaculture farms], and those in areas with no aquaculture,” he said.Stolt and his students will continue to sample, “until it becomes too cold.”Another goal of this project is to get an idea of how things would change if growers increase numbers of animals per area. Stolt will be collecting “bio-feces” from oysters reared at Roger Williams University to test on the four different soil types.“The ideal is high productivity with no environmental impacts,” said Stolt, noting that tradeoffs may include nitrogen influx from waste coming from too many organisms that can overload the system. “We’ll look at the bio-feces and benthic community response.”


Recognizing that some issues are best addressed at the regional scale, the Sea Grant Programs in the Northeast (New York, Connecticut, Rhode Island, MIT, Woods Hole, New Hampshire, and Maine), through the Northeast Sea Grant Consortium, have set aside funds (approximately $350,000) for social science research proposals that have relevance to

Coastal populations are growing, adding to the mounting strain on coastal ecosystems.This trend is particularly problematic given that habitats naturally distributed in coastal ecosystems that contribute a disproportionately large array of highly valuable ecosystem services.Jonathan Grabowski, an associate professor at Northeastern University, will be working to identify whether human vulnerability in coastal populations is tied to shoreline development and the integrity of coastal and marine habitats.This research seeks to identify the degree to which social capital, environmental connectedness, and adaptive capacity in coastal communities is linked to human and ecological resilience to provide managers with insights regarding 1.) the degree to which shoreline armoring influences perceptions of and acceptance of ocean-based wind energy development, and 2.) the efficacy of coastal policy at protecting shorelines and reducing human vulnerability in order to reveal which coastal shoreline policies should be implemented vs. those that are less successful

Research Projects 2012-2014
Research Projects 2010-2012  

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