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Consultation Workbook on the status change of the Western Silvery Minnow on the SARA List

PART 2: INFORMATION ABOUT THE SPECIES

Western silvery minnow

Status: Endangered

Last examined by COSEWIC: April 2008

Biology

The western silvery minnow is a small minnow with average total length between 75 and 125 mm. It is yellow with silver sides, a white belly and faint, broad, mid-dorsal stripe.

The western silvery minnow is typically found in the plains in quiet water with low velocity, such as in the backwaters and pools of larger streams. It prefers sandy bottoms but frequents areas of gravel, muck or debris-covered substrate. Spawning is believed to occur in May in shallow waters. Females begin spawning in their first year; males do not spawn until two years of age. The eggs are 1 mm in size, non-adhesive and hatch within a week in temperatures ranging from 13º to 20ºC. This species is known to form large schools of 50 to 100 fish and has a lifespan of up to four years.

Where are they found?

In Canada, the western silvery minnow is found only in the Milk River of southern Alberta.

How many fish are there?

The population size of western silvery minnows in Canada is unknown. Recent surveys collected a total of 2232 western silvery minnows at several new sites; however, due to its limited distribution the species may be sensitive to future anthropogenic and environmental disturbances.

Threats to the population

Given its limited distribution, the survival of the western silvery minnow in Canada may be particularly susceptible to a number of threats including siltation, changes in water flows and levels, prolonged drought and introduced pollutants.

COSEWIC Reason for Designation:

This small minnow species is restricted to the Milk River in Southern Alberta, a region characterized by drought conditions of increasing frequency and severity. While the future of flow regimes associated with the St. Mary’s diversion canal and proposed water storage projects are uncertain, consequences of these activities have the potential to significantly affect the survival of the species. Rescue effect from U.S. populations is not possible.

What will happen if this fish is listed as Endangered instead of Threatened on the SARA List?

Changing the SARA status of the Western Silvery Minnow from Threatened to Endangered does not change the protective prohibitions already in place. A recovery strategy for the Western Silvery Minnow has already been developed, and an action plan and identification of critical habitat will proceed as required for the existing Threatened status.