From the Government of Canada's Species at Risk Public Registry

From the Executive Summary:
"The Rocky Mountain Ridged Mussel is a freshwater mollusc and was listed as a species of special concern under the Species at Risk Act (SARA), in July 2005. This large freshwater bivalve has a trapezoidal shell. The most distinctive feature of the shell is a prominent posterior ridge running almost parallel with the anterior margin, from the umbo to the angular basal posterior margin of each valve.  The posterior length of the shell exceeds the anterior length of the shell.

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The current range of the Rocky Mountain Ridged Mussel includes the Okanagan River watershed, from the northernmost record in Vernon to the southernmost record of a shell found in the Osoyoos area.  The range extent will be expanded if occurrences are found in the Kootenay or Columbia River watersheds, or the historic record from Vancouver Island is confirmed.

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The management objectives for the Rocky Mountain Ridged Mussel are: 1) By 2015, address knowledge gaps about the life history, provincial range and threats to the Rocky Mountain Ridged Mussel; 2) By 2015 inventory 75% of potential littoral habitat within the Okanagan River watershed, with standardized protocol for habitat and threat information collected at each site searched; 3) By 2015, demonstrate an increased number of stewardship activities initiated and completed for land managers and public users of habitats occupied by the Rocky Mountain Ridged Mussel; and 4) As research and inventory results on Rocky Mountain Ridged Mussel become available, incorporate into land-use planning to inform future threat mitigation and land use protection."

See the full report [PDF file hosted at the Species at Risk Public Registry website].