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Research Document - 2011/109

Recovery Potential Assessment for Rocky Mountain ridged mussel (Gonidea angulata)

By R.B. Lauzier and L. Stanton


The Rocky Mountain ridged mussel (Gonidea angulata) is a freshwater bivalve mollusc that reaches the northern extent of its global distribution in southern British Columbia. Gonidea angulata is restricted to the Okanagan Basin with small aggregations present in the northeast and southwest areas of Okanagan Lake in addition to a few individuals encountered in Vaseaux Lake and the Okanagan River. Recent broad-brush surveys indicate that their range and distribution is decreasing and their numbers are in decline. The preponderance of large adult mussels and the apparent absence of small and/or young juveniles could indicate a relict or ageing population with limited reproductive potential. Potential or known threats and their impacts to habitat such as channelization of the Okanagan River, dams and weirs, development of shoreline and littoral zones, pollutants, introduced species such as Eurasian watermilfoil and dreissenid mussels, are evaluated and mitigation measures are discussed. Recommendations for future research are provided in an attempt fill knowledge gaps and to meet recovery objectives to sustain viable populations and prevent the extirpation of the Rocky Mountain ridged mussel in Canada.

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