MILK RIVER WATERSHED COUNCIL CANADA OVERWINTERING HABITAT STEWARDSHIP PROJECT – PHASE II

Winter is critical time for riverine aquatic species across Canada, specifically within the Milk River in southern Alberta. Survival through extended sub-zero winter temperatures is primarily dependent on sustainable and consistent sources of dissolved oxygen and foraging potential. The Milk River is generally known to provide variable flow conditions throughout the year and is particularly susceptible to periodic losses of surface flow in certain reaches of the system. Winter ice cover introduces another dimensional variable seasonally affecting river flows and overall water connectivity. Considering the river dynamics of the Milk River, winter refugia are critical to general fish survival in the watershed. Compounding the concerns, are the occurrences of several fish species at risk (SAR), including the western silvery minnow (Hybognathus argyritis) and the eastern slope Rocky Mountain sculpin (Cottus bairdii/Cottus sp.), both listed as Threatened within the Milk River watershed. The western silvery minnow is nationally endemic to the Milk River, whereas the eastern slope Rocky Mountain sculpin is endemic to the Milk River, small reaches of the adjacent St. Mary’s River (both in Alberta), and the Flathead River (in British Columbia). In order to support the instream flow needs of the Milk River, the Milk River Watershed Council of Canada (MRWCC) received funding to conduct a two-year Habitat Stewardship Program Species at Risk Project from Fisheries and Oceans Canada for stewardship work within the Milk River watershed. One of the selected projects included the Milk River Over-Wintering Habitat Stewardship Project (OWHP), which primarily focused on identifying key over-wintering refugia on the Milk River, aquatic life that may frequent these locations and general habitat conditions. The OWHP was to give special attention to the western silvery minnow and the eastern slope Rocky Mountain sculpin to support targeted voluntary habitat stewardship projects in the watershed, where necessary.