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Conservationists are seeing mussel die offs across the Pacific Northwest


Media contacts:

Emilie Blevins, Senior Conservation Biologist, Xerces Society for Invertebrate Conservation
[email protected] 

Sarina Jepsen, Director of Endangered Species and Aquatic Programs, Xerces Society for Invertebrate Conservation
[email protected]  |  971-244-3727

PORTLAND, Ore. (August 18, 2020)---The Xerces Society for Invertebrate Conservation today filed a petition seeking Endangered Species Act protection for the western ridged mussel (Gonidea angulata).

The western ridged mussel can live for many decades in rivers and streams in Oregon, Washington, Idaho, California, and Nevada. However, western ridged mussels have been lost from 43% of their historic range. Western ridged mussels are also no longer found throughout much of their former southern range including in large areas of California.

“The western ridged mussel has been lost from many of the rivers and streams it used to inhabit,” said Emilie Blevins, Senior Conservation Biologist at the Xerces Society. “The few remaining populations are likely to go extinct without Endangered Species Act protection.”

Several populations in Oregon and Washington have experienced sudden die-offs that have reduced populations considerably. These die-offs have occurred in rivers across the region—such as the Chehalis River in Washington and the Crooked River in Oregon—and have resulted in devastating effects on beds of the western ridged mussel and other species, often with thousands of mussels killed outright over the course of a single summer and spanning tens of river miles. There is still a lot we do not know about these die offs including the extent and the cause. 

Western ridged mussels face a variety of threats that include the recent die-offs mentioned above as well as habitat destruction and degradation, impacts to water quality and quantity such as impoundment, abstraction, and pollution, warming rivers due to climate change, inadequate protection from recreational harvest, and the potential for introduction of invasive species like zebra mussels.  Mussels often look like rocks and can be hard to see. As such they can be unintentionally destroyed by in-water construction work—even, unfortunately, when Pacific Northwest rivers are restored for salmon. Recovery can take decades.

Freshwater mussels perform critical functions in freshwater ecosystems that contribute to clean water, healthy fisheries, diverse aquatic food webs and biodiversity. The richness of aquatic life promoted and supported by freshwater mussel beds is analogous to coral reefs, with mussels providing both structure and habitat for other animals, cleaning and clearing water, and enhancing riverbed habitat. Freshwater mussels are also significant to some tribes in the Pacific Northwest as a traditional cultural resource.

“Freshwater mussels are like the lungs of a river,” said Sarina Jepsen, Endangered Species Program Director at the Xerces Society. “Yet, they are often overlooked and inadvertently destroyed.”

The Xerces Society has been working for more than a decade to understand and conserve the western ridged mussel and other freshwater mussels that occur in western states. We conduct inventories and monitoring to fill data gaps, work with other biologists and land and water managers to identify and protect fragile mussel beds, work with restoration professionals to protect and or move mussels during in-water river restoration and construction work, and are currently investigating the causes of enigmatic mussel die-offs.


Read the ESA petition:

Learn more about our work to protect western freshwater mussels

Download detailed conservation guidance on mussel-friendly restoration of rivers



The Xerces Society is a nonprofit organization that protects the natural world by conserving invertebrates and their habitat. Established in 1971, the Society is a trusted source for science-based information. Although widely known for protecting bumble bees and monarch butterflies, Xerces plays a leading role in the conservation of freshwater mussels and other aquatic invertebrates, especially in western North America. Our team draws together experts from the fields of habitat restoration, entomology, education, pesticides and conservation biology with a single passion: Protecting the life that sustains us.

To learn more about our work, please visit or follow us @xercessociety on Twitter, Facebook or Instagram.