When University of Rhode Island researchers slipped beneath the surface of the Moosup River recently, they did not expect to find a living freshwater mussel community. The discovery marked the first documented record of freshwater mussels in the river in more than three decades and included rare native species considered sensitive indicators of river health.
Graduate students Jamie Bucholz and Mallory Malz in URI's Department of Natural Resources Science identified the mussel community during a survey of the river, which flows through northeastern Connecticut and western Rhode Island.
It's a major milestone and a rare piece of good news for one of the world's most overlooked endangered animal groups.
The research is part of a statewide effort led by Bucholz and Shelby Rinehart to better understand where native freshwater mussels still persist. The project brings together the Narragansett Bay Estuary Program, the Rhode Island Department of Environmental Management and the Massachusetts Division of Fisheries and Wildlife.
"Mussels are the unsung heroes of our river ecosystems," Bucholz said. They filter water, stabilize sediments, cycle nutrients and create habitat for other aquatic species.
"While Rhode Island is the Ocean State, our freshwater systems are also valuable habitats, and what happens in the upper watershed ultimately flows downstream to the bay," said Rinehart, an assistant professor of natural resources science at URI.
"Finding freshwater mussels in the Moosup River is like getting a glowing health report for the river," Bucholz added. "Because mussels are incredibly sensitive to pollution and heavy metals, their presence suggests that the water quality remains healthy enough to support a complex, interconnected community of native wildlife."
The team identified species including the triangle floater and creeper, both of which are native mussels rarely found in healthy numbers. The discovery provides a valuable benchmark for freshwater restoration efforts across Rhode Island and the broader Atlantic coast.
Tiny hitchhikers
To reproduce, a freshwater mussel has to pull off one of nature's most elaborate deceptions.
Baby mussels, called glochidia, begin life as tiny larvae that must attach themselves temporarily to the gills of a fish. To make that happen, some adult mussels use an extraordinary deception: They extend a fleshy mantle lure from their shell that resembles a small fish or crayfish, complete with false eyespots and tail-like movement.
"A curious predatory fish swims down to bite the 'minnow,' and bam—the mussel safely deposits its larvae onto the fish's gills," Bucholz said. "It's one of the most brilliant deceptive optical illusions in the animal kingdom."
The young mussels remain attached as they transform into juveniles before dropping into a new stretch of stream, where they burrow into sediment and grow.
This unusual life cycle makes connected waterways essential for mussel survival. Dams, undersized culverts and other barriers can prevent fish hosts from moving through rivers, limiting the ability of mussel populations to spread and recover.
Searching for survivors
The Moosup River discovery contrasts sharply with other survey sites. Researchers have examined rivers across the state, including sections of the Pawtuxet River, where they found no evidence of living mussels.
"Rhode Island has done a great job investing in marine ecosystems, but freshwater systems have historically lagged behind," Bucholz said. "These freshwater habitats are directly connected to our coastal waterways and have the potential to influence Rhode Island's future water quality, water quantity and blue economy."
The surveys are part of a larger regional collaboration with the Philadelphia Water Department exploring how freshwater mussels can be restored in both natural rivers and novel habitats such as constructed stormwater ponds. By identifying where healthy populations remain, researchers can determine where restoration efforts are most likely to succeed.
"Our next steps really focus on trying to understand what the mussels are actually doing for us in these habitats," said Rinehart. "We're looking at how these mussels are helping to improve water quality through filtration and stabilize stream beds to prevent erosion. Our long-term goal is to understand how we could restore mussels to both increase population densities and increase the effects of the services that they provide."
A call to explore Rhode Island's hidden rivers
The team plans to continue surveying waterways throughout Rhode Island in search of all eight native freshwater mussel species known to occur in the state.
Landowners with river frontage are encouraged to consider granting safe access for future surveys, and volunteers interested in assisting with fieldwork are welcome to get involved. For a small, easily missed creature, the freshwater mussel turns out to have a lot riding on it.
Who's behind this story?
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Citation: Researchers discover rare freshwater mussels in Moosup River (2026, July 16) retrieved 17 July 2026 from https://phys.org/news/2026-07-rare-freshwater-mussels-moosup-river.html
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