Western Pearlshell

The Western Pearlshell (Margaritifera falcata) is a freshwater mussel species native to river systems west of the Rocky Mountains in North America, as far north as southern Alaska and as far south as central California. This mussel shows preference towards cold, clean creeks and rivers occupied by salmonids (which act as glochidial host fish for this species). Across their range, freshwater mussels are facing serious declines, the Western Pearlshell not excepted. The Western Pearlshell is in decline in various areas within its range, and the comparison of historical and current records suggest that its populations are declining in British Columbia as well. Freshwater mussels are filter feeders and are therefore vulnerable to environmental factors (e.g. changes in water quality), making them valuable indicators of ecosystem health. Threats to the Western Pearlshell include reduced water quality (due to impacts such as eutrophication, acidification, and chemical and heavy metal pollution), as well as damming, channel modification, climate change, low water levels, aquatic invasive species, and decline in host fish populations.

A Rocha assessed the status of Western Pearlshell in the Little Campbell River in 2009 and again in 2015 in partnership with Dr. Jon Mageroy and the University of British Columbia Okanagan.  Surveys were conducted at suitable sites and sites known to be occupied. Results to date suggest that there has been a decline in the population since 2009 due to reduced ecosystem health prior to 2009. However, the results also suggest that ecosystem health has improved in recent years, which may allow for maintenance of a stable population in the Little Campbell River. A Rocha plans to continue periodic surveys of Western Pearlshell in the Little Campbell River,  augmented by the assessment of host fish usage studies. The goals of these surveys are to improve understanding of the Western Pearlshell in the Little Campbell River, provide an indication of overall watershed health, and inform watershed-based conservation management measures.

Conservation Status

*S: Subnational status; *5: demonstrably widespread, abundant, and secure.