Once populous over a wide territory, eastern sand darters have been dwindling in numbers since the start of the 20th century—and have vanished entirely from some of their original territory. In Canada, this species has been found in Lake Huron, Lake Erie and Lake St. Clair, and in the St. Lawrence River and Lac Champlain. Specimens are still found in Lake Erie and Lake St. Clair, and in a number of rivers in southwestern Ontario and Quebec. Deteriorating water quality is suspected to have caused the decline and in some cases extirpation (local extinction) of this species in Montreal and Chateauguay, Quebec. The eastern sand darter is protected under the federal Species at Risk Act (SARA).