Imagine swimming down to a riverbed. The water sweeps on above you, but, down here, there’s stillness. As you peer down, you see a jigsaw puzzle of smooth stones nestled perfectly together, edge to edge, symmetric and dark. But on a second glance, you realize they aren’t stones. This is, in fact, an increasingly rare treasure to find in Oregon’s rivers: freshwater mussels. To the untrained eye, they may be overlooked, but their presence carries good news of the river’s health and a flourishing underwater ecosystem.
Emilie Blevins, Senior Endangered Species Conservation Biologist and Freshwater Mussel Lead for Xerces Society for Invertebrate Conservation, has seen freshwater mussels countless times, but she still gets excited every time she dives under a river’s current and finds them amongst the riverbed and rocks. “I always knew I wanted to work with animals, so in college, I sought out research opportunities,” says Blevins. “My very first one was with freshwater mussels and snails. I thought they were so cool because they have this totally unique life cycle that I got to see firsthand. I was absolutely amazed—and that always stuck with me.”
Her summer mornings in the field often include putting on a dry suit and a snorkel to assess freshwater mussel populations and distributions. However, the populations she often sees are not carpets of mussels blanketing the riverbed, but rather populations struggling to hang on.
Freshwater mussel populations have been quietly declining over the past few decades, driven by a mix of habitat destruction, pollution, and changes to river flows from human-made structures like dams. Unfortunately, the full scope of these declines is hard to measure as these overlooked species have not received much research attention, despite their critical role in maintaining river health.
Freshwater mussels filter water, stabilize riverbed sediments, and create habitat for other aquatic life. As they disappear, the rivers they support become more fragile, impacting native fish and even the people who rely on these waterways. Researchers like Blevins, alongside groups like the Xerces Society, Willamette Riverkeepers, and the Bureau of Land Management, are working to fill knowledge gaps, monitor populations, and restore mussel habitat. Their efforts are grounded in the belief that reviving these quiet ecosystem cleaners can strengthen Oregon’s freshwater systems in the face of a changing climate.
Fondly referred to as “the liver of the river” by Blevins, freshwater mussels trap pollutants and cycle nutrients to help sustain entire ecosystems. They can live for up to 100 years burrowed in the bottom of the streambed, filtering eight to fifteen gallons of water every day. Mussels are “fundamentally part of the river, absorbing and filtering any pollutant that ends up in our river,” says Blevins. While this results in cleaner river ecosystems, it also means freshwater mussels are especially vulnerable to human pollution, such as oil spills, agricultural runoff, and sewage. “There's not really a separation between the animal and the ecosystem as the river is them and they are the river,” says Blevins.
Any loss of mussel beds indicates something is wrong in a river. The “way that we treat our rivers directly affects whether or not we will have mussels in the future,” says Blevins. She recalls how she recently visited a thriving mussel bed she first saw two years ago in a river in Washington State, only to find “half of them dead and dying.” Blevins views these lived data points as a “driving force” in her work wanting to “ensure that doesn't happen anywhere else.”
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One way to do that is to restore healthy habitats the mussels need for survival. Organizations such as Xerces Society, Wilamette Riverkeeper, Mckenzie River Trust, and The Nature Conservatory have made significant efforts to restore mussel habitats in rivers like the Willamette and the McKenzie rivers for over a decade. Their work has included a variety of endeavors such as improving the water quality, relocating the mussels, and restoring floodplains and riparian zones — areas along the riverbank that connect water with the land, helping to maintain a healthy ecosystem. Mussels rely on these zones for protection, stabilizing them in return. With over 300 mussel species documented, nearly 35 have gone extinct. However, in areas where restoration is being done, mussel populations have had notable increases as a result, however, specific numbers are still being gathered.
Blevins herself has participated in restoration work through her active involvement with Xerces Society and McKenzie River Trust, where she hopes to see more habitat restoration activities within the Willamette Valley that help to revitalize riparian zones and riverbanks.
Although freshwater mussel populations are in decline, people like Blevins see this reality as a motivator to protect them. She believes every Oregonian can play a part, recommending that if you see a mussel shell along the river, that’s a sign of life — likely a live mussel nearby. Share those observations on platforms like iNaturalist to help track and protect these vital species. For those interested in restoration involvement, Blevins recommends exploring resources on the Xerces Society website to learn how you can help. Through the combined efforts of research, restoration, and education, she emphasizes that these “powerhouses of the river” can have a place to thrive, reminding us of the wonder and resilience of the Willamette Valley.