Status of the Northern Riffleshell, Epioblasma torulosa rangiana (Bivalvia: Unionidae), in Ontario and Canada

The Northern Riffleshell freshwater mussel has declined dramatically in North America over the last 100 yr. It now occupies only 5% of its former range and is recognized as an endangered species in the U.S. and at risk in Canada. Factors contributing to the population decline include introduction of the zebra mussel and agricultural impacts that degrade mussel habitat. Existing populations occur in regions subject to intense agriculture and forestry, making the mussels susceptible to siltation and chemicals in runoff. In Canada, the Northern Riffleshell is found only in the middle reaches of the Sydenham and Ausable Rivers of Ontario, and the only North American population that still reproduces occurs in the Sydenham River. Protection of this population is critical for survival of the species. Extinction could occur within 10 yr unless protective measures are taken.