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Oyster Study Aims to Boost Production in Long Island Sound, Housatonic

"The goal is to expand oyster growth and cultivation in this critical area while also protecting public health and oyster habitat," a state agriculture official said.

DoAg aquaculture scientist Dave Lamoureux pulls in a device called a fluorometer that measures wastewater-tracking dye near oyster beds in L.I. Sound and the Housatonic River. (Photo: Connecticut Department of Agriculture)
DoAg aquaculture scientist Dave Lamoureux pulls in a device called a fluorometer that measures wastewater-tracking dye near oyster beds in L.I. Sound and the Housatonic River. (Photo: Connecticut Department of Agriculture)
By Steve Jensen
Connecticut Department of Agriculture

[Editor's note: This article and the photos accompanying it originally were published in the Connecticut Weekly Agricultural Report issued by the state Department of Agriculture. The article, including the pictures, are reprinted here with permission and the full issue of the emailed newsletter is attached.]

The densely-packed shoreline dotted with industrial and residential complexes at the junction of the Housatonic River and Long Island Sound might seem an unlikely place for oysters to flourish.

But the Eastern Oyster is indeed thriving in the area, and a recent DoAg study aims to increase the harvest while protecting the oyster beds from any potential contamination from nearby sewage treatment plants.

It was conducted over the past two weeks as part of an ongoing oyster resource-enhancement project developed by Director David Carey and staff at DoAg’s Bureau of Aquaculture.

“The goal is to expand oyster growth and cultivation in this critical area while also protecting public health and oyster habitat through science-based management practices,” Carey said.

The Eastern Oyster is the state’s official shellfish. In addition to drawing a premium price for their taste and texture, they also filter up to 100 gallons of water a day and so serve to cleanse the water where they live.

The study included use of a harmless red dye that was injected into the effluent outflow of water pollution control facilities in Milford and Stratford so that the wastewater could be tracked as it enters the river and the Sound.

That will allow scientists to determine where oysters can be safely harvested, and what areas of the river should be avoided.

“Oysters prefer a little less salinity so they thrive at the mouths of rivers where they meet the ocean,” said Donald Ullstrom, a shellfish specialist with the U.S. Food & Drug Administration (FDA). “Most of the Sound is actually pretty clean and this estuary is a perfect place for them to grow.”

Scientists and engineers from DoAg, the U.S. Environmental Protection Agency’s New England Regional Laboratory, and staff from the FDA Shellfish Sanitation Program conducted the study.

On May 7, the team injected 27 gallons of Rhodamine WT dye over a 12-hour period into the outflow from the water pollution control facility in Stratford.
Most dissipated in the current over the next several hours.

But some lingered until the next morning in the still waters around docks just south of the treatment facility as the team set off on a DoAg boat to track the dye headed for the Sound.

A cylindrical device called a fluorometer – attached to a rope and a bright orange buoy – is lowered into the water and trails about 20 feet behind the boat, recording the levels of dye, which correspond to the levels of bacteria in the area.

A GPS computer screen in the boat’s small cabin showed the concentrations of dye detected by the fluorometer in colors ranging from green for low levels, yellow for moderate and red for the highest.

“We’re looking to see where the dye trail ends,” said Yaping Ao, an FDA engineer who assisted in the study. “Turn west and let’s see what happens,” she instructed DoAg boat Captain Tom Barrell.

He steers the boat toward the natural “plume” marking the border where fresh water meets salty. Levels of the dye — and therefore the wastewater it is tracking — decreased considerably as soon as the boat crossed the line.

“It dropped down as soon as we hit it,” Barrell said.

That caused the tracking line on the GPS computer screen to transition from a moderate yellow to a lower-level green, indicating that wastewater rapidly dilutes when it reaches the edge of the Sound.

The team also lowered six cages of oysters — three each in the Sound and the river — equipped with dye-tracking equipment and sensors to record water depth, temperature and salinity levels to which the oysters are exposed in each area.

Shellfish samples and other data will be shipped to the FDA’s Dauphin Island Laboratory in Alabama to be analyzed for bacterial and viral indicators including fecal coliform, male-specific coliphage, and norovirus. That will allow scientists to determine the areas where shellfish are significantly impacted by discharge from the treatment plants.

The sophisticated software and equipment used in the study represents a huge progression from only a few years ago, when samples were taken by dipping a beaker in the water by hand and recording the location on a paper map.

“This technology provides us with much more specific information used to determine where oysters can be safely harvested,” said Kristin Derosia-Banick, an environmental analyst with DoAg’s aquaculture bureau.

As the boat slowly criss-crossed the area, as many as five oysters boats worked nearby. Oysters are pulled off the river bottom by a dredge, and men on the deck pick out ones that are proper size and toss the others over the side.

The area is intensively used for harvesting “seed” oysters to be transplanted elsewhere to grow to market size. Larger, mature oysters must remain in the river.

One of the study’s objectives is to develop management practices that would potentially allow the harvest of both seed and mature oysters from areas of the river that have been identified as appropriate.

Oysters of any size will be required to be transplanted to offshore harvest areas for a period of time, allowing the oysters to cleanse themselves of bacteria and viruses that can potentially make people ill.

DoAg environmental analyst Dave Lamoureux Jr. said oysters are becoming more attractive as other shellfish species in the area decline.

“Lobsters are down, conch is down,” Lamoureux said. “More of these guys are turning to oysters because they want to keep working on the water — that’s their livelihood.”

DoAg Commissioner Steven K. Reviczky said the study is another tool the agency is using to create more opportunities in aquaculture and to encourage the use of best practices in the approximately 80,000 acres of shellfish beds between Greenwich and Stonington.

“The Housatonic’s junction with the Sound is one of the state’s most important natural oyster-producing areas,” Reviczky said. “Our goal is to not only preserve this key aspect of our farming industry, but to expand it for the benefit of shellfishermen, consumers and the state’s economy.”

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