The blind hypogean asellid Salmasellus steganothrix Bowman (Crustacea: Isopoda) is reported from a cave spring located on the eastern slopes of the Rocky Mountains of Alberta, Canada. This is the only known aquatic isopod from Alberta and represents an extraordinary range extension for North American hypogean isopods. Water temperatures of the spring are almost constant, near 7 °C, for about 9 months of the year, but fluctuate because of snow melt in May, June, and July. Dissolved oxygen is often less than 1 mg/1 during the winter, and the isopod has not been collected from December through May, even though the spring is sampled at about monthly intervals. The distribution record is considered to be evidence supporting the existence of unglaciated low-elevation refugia on the eastern side of the Canadian Rocky Mountains during Wisconsin time.
