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Western Pearlshell Mussel


Western pearlshell mussel (Margaritifera falcata)

Principal Biologist(s)

Carter Kruse

Project Location

Southwestern Montana; Cherry Creek, Flying D Ranch, MT

Conservation Problem

Range-wide declines are thought to be primarily due to water quality concerns (sedimentation, agricultural run-off, increasing temperatures), habitat fragmentation (dams, water diversion), and declines or loss of suitable host fish species (e.g., native salmonids).

Conservation Status

Historically found across the northwestern United States, this species remains widespread in geographic area, but regional and localized declines are concerning.  Documented, localized, watershed level extirpations are common. Idaho, Oregon, California, and Montana all consider the species either potentially at risk or at risk due to limited or declining population numbers (S2 or S3 NatureServe Conservation ranking). The species is likely extinct in Utah. Numbers appear more secure in Washington, but declines are suspected. The US Forest Service Region 1 considers it a Sensitive Species, and Montana Fish, Wildlife, and Parks has designated it a Species of Greatest Conservation Need.

Project Goals & Objectives

The goal of this project is to establish a large and persistent population of Western pearlshell mussels (WPM) in Upper Cherry Creek that can provide individuals to other WPM restoration projects.  This effort includes three primary objectives to:

  • Conduct the experiment and research necessary to establish accepted protocols for translocation and restoration of WPMs in Montana.
  • Establish a reproducing population of more than 250 WPMs in upper Cherry Creek.
  • Provide WPMs for restoration elsewhere in the Madison basin.


Project Background