Fawnsfoot (Truncilla donaciformis) COSEWIC assessment and status report: chapter 1

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Assessment Summary

Assessment Summary – April 2008

Common name: Fawnsfoot

Scientific name: Truncilla Donaciformis

Status: Endangered

Reason for designation: This freshwater mussel is widely distributed in central North America, with the northern portion of its range extending into the Lake Erie, Lake St. Clair and lower Lake Huron drainages of southwestern Ontario. It appears to have always been a rare species in Canada, representing < 5% of the freshwater mussel community in terms of abundance wherever it occurs. Approximately 86% of historical records are in waters that are now infested with zebra mussels and therefore uninhabitable. Zebra mussels, which were accidentally introduced into the Great Lakes, attach to the shells of native freshwater mussels, causing them to suffocate or die from lack of food. The species has declined dramatically and has been lost from four historical locations resulting in a 51% reduction in its range. It is now found in only five widely separated locations, two of which represent single specimens. In two locations, the species' distribution may be limited by the presence of dams that restrict the movements of the frehswater drum, the presumed fish host of the juvenile mussels. Poor water quality resulting from rural and urban influences poses an additional continuing threat.

Occurrence: Ontario

Status history: Designated Endangered in April 2008. Assessment based on a new report.