Western Freshwater Mussels

Freshwater mussels are experiencing a dramatic decline; seventy-one percent of all species of North American freshwater mussels are considered endangered, threatened, or of special concern, representing one of the most at-risk groups of animals in the United States (Williams et al. 1993). The decline of freshwater mussels has been well studied in eastern North America, but has received very little attention in states west of the Rocky Mountains. While there is a paucity of information on the biology and status of western freshwater mussels, anecdotal evidence suggests that these animals are experiencing population declines due to habitat alteration or destruction and loss of host fish species.

To better understand the status and distribution of these animals, The Xerces Society recently completed a Status Review of three of the most imperiled species and species groups of freshwater mussels that inhabit the U.S. west of the Rocky Mountains: the western pearlshell (Margaritifera falcata), the western ridged mussel (Gonidea angulata) and the California floater/winged floater group (Anodonta californiensis/Anodonta nuttalliana). We conclude that severe declines have occurred in the parts of the ranges of each of the species or species groups reviewed, and all three are of conservation concern.

Native freshwater mussels have immense ecological and cultural significance. As filter-feeders, they can substantially improve water quality, which benefits aquatic ecosystems and, ultimately, humans. Freshwater mussels can benefit native fish by making food more visible and bioavailable to the fish. These animals can be highly sensitive to environmental changes and thus have great potential to be used as indicators of water quality. Freshwater mussels were historically important sources of food, tools, and other implements for many Native American tribes. Native Americans in the interior Columbia Basin have harvested these animals for at least 10,000 years.

Learn more about mollusks and different Western freshwater mussels here.



PNW Native Freshwater Mussel Workgroup

Visit the Pacific Northwest Native Freshwater Mussel Workgroup website, Facebook page, or Freshwater Mussels of the Western US iNaturalist project for more information.

Anodonta nuttalliana

Western Freshwater Mussel Database

The Xerces Society and the Confederated Tribes of the Umatilla Indian Reservation have compiled a database of western freshwater mussel records for the following species and clades: Anodonta californiensis/nuttalliana, A. oregonensis/kennerlyi, Gonidea angulata, and Margaritifera falcata. Copies of this database are available to researchers upon request

For a full list of contributors and data sources used for this database, click here.


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Mussel bed composed of Anodonta sp. and Gonidea angulata, Middle Fork John Day River, Oregon. Copyright CTUIR freshwater mussel project.