Pacific Northwest Freshwater Mussel Workgroup

About the Pacific Northwest Freshwater Mussel Workgroup

Founded in 2003, the purpose of the Pacific Northwest Freshwater Mussel Workgroup is to Ensure that freshwater mussel research, management, and educational activities are coordinated, prioritized, and are consistent with identified information needs.” Learn More

Oregon floater (Anodonta oregonensis) Photo: Patrick Norton

Oregon floater (Anodonta oregonensis) Photo: Patrick Norton

The status of the seven species of freshwater mussels native to the Pacific Northwest has received very little attention, despite the fact that freshwater mussels are considered to be the most endangered group of animals in North America.

What are freshwater mussels and why do they matter?

Freshwater mussels are a vital but often unrecognized component of many aquatic ecosystems and have immense ecological and cultural significance. As filter-feeders, they substantially improve water quality contributing to the overall health of aquatic ecosystems. Additionally, they benefit native fish by making food more visible and bioavailable, and provide nutrients and living space for other aquatic invertebrates.


Freshwater mussels are the most imperiled wildlife in the world.

Over 75% of North America’s species are listed as endangered, threatened, or of special concern. Like our native salmonids, freshwater mussels are declining due to habitat degradation and fragmentation caused by dams, water pollution, and reduced streamflow. These animals can be highly sensitive to environmental changes and should not be ignored as indicators of water quality and ecosystem degradation. Recently the International Union for Conservation of Nature (IUCN) published updated statuses for Western North American freshwater mussels on the Red List of Threatened Species. Two species, the western ridged mussel (Gonidea angulata) and the winged floater (Anodonta nuttalliana), were categorized as Vulnerable, the western pearlshell (Margaritifera falcata) as Near Threatened, and the Oregon floater (Anodonta oregonensis) as Least Concern… Learn More