On August 18, 2020, the Xerces Society for Invertebrate Conservation filed a petition to list the western ridged mussel as an endangered species under the Endangered Species Act (ESA).

The western ridged mussel (Gonidea angulata), is found in the rivers and streams of Washington, Oregon, Idaho, California, and Nevada, but in less than 60% of its historic range. Several populations of mussels in Washington and Oregon have recently experienced sudden die-offs, reducing populations even further. The die-offs have occurred in rivers across the region—such as the Chehalis River in Washington and the Crooked River in Oregon. The results are devastating mussel beds, often with thousands of mussels killed over the course of a single summer and spanning tens of river miles. The cause and extent of these die-offs is not well understood.

Like other freshwater mussels, the western ridged mussel performs critical functions in freshwater ecosystems that contribute to clean water, healthy fisheries, diverse aquatic food webs, and biodiversity.

The Xerces Society, along with the U.S. Fish and Wildlife Service and the Confederated Tribes of Umatilla Indian Reservation, have been working on several projects over the last two decades in order to learn more about this species. The recent die-offs, however, have alarmed scientists at the Xerces Society, prompting them to file this petition based on the belief that ESA protections are necessary in order to learn more about the species and its threats before it is too late for recovery.

The western ridged mussel is not produced or sold commercially, but recreational harvest by the general public does occur. The mussels are important both historically and culturally for the Umatilla Tribes, in particular. The tribes traditionally boiled or dried the mussels in the fall and stored them over winter as a supplementary food supply. Their shells were also used for jewelry, beads, ornaments, and ceremonies.

The Xerces Society formally petitioned to list the western ridged mussel as an endangered species under the Endangered Species Act, 16 U.S.C. § 1531 et seq. The petition was filed under 5 U.S.C. 553(e) and 50 CFR 424.14(a), which grants interested parties the right to petition for issue of a rule from the Secretary of the Interior. The petition sets in motion a process placing definite response requirements on the U.S. Fish and Wildlife Service and specific time constraints upon those responses. 16 U.S.C. § 1533(b). A finding by the U.S. Fish and Wildlife Service regarding whether the petition contains substantial information to warrant a full status review is required within ninety days.