Stillaguamish Tribe tracking freshwater mussels

The Stillaguamish Tribe is documenting the western pearlshell mussel in the Stillaguamish watershed to track how the once plentiful but now threatened riverine species is faring amid warmer stream temperatures and habitat degradation.  

“The tribe’s natural resources department is doing the work as funding and time permits,” said Franchesca Perez, Stillaguamish Tribe shellfish biologist. Perez hopes more funding will be available for study, monitoring and habitat improvement if another freshwater mussel species—the western ridged—is listed under the federal Endangered Species Act.

Shellfish biologists surveying western ridged mussels could also survey western pearlshell and floater mussels while doing the work, Perez said. All three freshwater mussels are found in western Washington, although only the western pearlshell and floater species have been found in the Stillaguamish watershed, Perez said.

The Xerces Society for Invertebrate Conservation petitioned the U.S. Fish and Wildlife Service in August 2020 to list the western ridged mussel as an endangered species. The federal agency recently determined that there’s enough data supporting the listing, and it will review the mussel’s status.

While the other two mussel groups are not considered to be endangered, their populations are considered precarious. The western pearlshell mussel is rarely found in its historical range and is listed as a “species of greatest conservation need” by the state of Washington. Floaters (genus: Anodonta) are not listed, but their populations have been declining, according to The Xerces Society.

The western ridged mussel, one of three freshwater mussel species native to western Washington, is a candidate for federal endangered species listing. Photo: U.S. Fish and Wildlife Service

Stillaguamish natural resources staff found western pearlshell mussels in the Stillaguamish watershed in 2017 during a creek restoration project. Since then, they have attended freshwater mussel field training and symposiums, joined the Pacific Northwest Freshwater Mussel Workgroup, and adopted best management practices for freshwater mussels during restoration project planning and implementation, Perez said.

In summer 2021, the tribe offered a freshwater mussel workshop to regional tribes and other local governments, funded by the U.S. Bureau of Indian Affairs’ Tribal Climate Resilience Program.

“Each summer, natural resources staff also provide a presentation to department leadership, new hires and tribal youth interns about this important aquatic health indicator species,” Perez said. “When capacity allows, we bring our interns out on stream snorkel surveys. The mussels are so cryptic, it is like an Easter egg hunt underwater.”

Mussel larvae get to their rearing areas by hitching a ride on the gills and fins of returning salmon. They drop off at the right time and burrow into the sediment, maturing into filter feeders that improve water quality.

It’s been a long time since Coast Salish people have been able to harvest freshwater mussels, which Lushootseed speakers know as tulqw.

“The Washington Department of Fish and Wildlife now prohibits harvest of any freshwater mussels or clams,” Perez said.

Sauk-Suiattle Tribe natural resources director Jason Joseph said the harvesting of freshwater mussels is only something he heard about from his grandmother. He’s seen freshwater mussels in the Sauk River behind the reservation, “but I’ve never harvested them,” he said.

Treaty tribes elsewhere in western Washington have taken steps to protect vulnerable freshwater mussel populations. The Lower Elwha Klallam and Jamestown S’Klallam tribes relocated 5,000 freshwater mussels in 2008 that were threatened by work to remove the Elwha and Glines Canyon dams. And in 2009 the Squaxin Island Tribe documented freshwater mussel populations on Little Skookum Creek south of Shelton.

Above: Western pearlshell mussels were found during a creek restoration in the Stillaguamish watershed in 2017. Photo: Stillaguamish Tribe Natural Resources Department. Story: Richard Walker

Freshwater mussels in western Washington

Three types of freshwater mussels are found in western Washington. Historically, Indigenous people harvested freshwater mussels for food and used their shells for decorative and utilitarian objects. Today, however, freshwater mussel populations have declined to the point where they cannot be harvested. 

  • Western ridged mussel: Candidate for federal Endangered Species Act listing. 
  • Western pearlshell mussel: Extinct in much of its historical range. Listed as a species of greatest conservation need by the state of Washington. 
  • Floater: Not listed, but its population has been declining, according to The Xerces Society for Invertebrate Conservation.