An Isolated Population of Arctic Char (Salvelinus alpinus) Inhabiting a Warm Mineral Spring Above a Waterfall at Cache Creek, Northwest Territories

Cache Creek Spring provides an unusual overwintering habitat for a population of Arctic char (Salvelinus alpinus) isolated above a falls impassable to fish moving upstream. During winter, water temperatures (14–16 C) and dissolved solid concentrations (approximately 2600 ppm) are high and oxygen concentrations (0.2–6.8 ppm) are low. Arctic char in the springs differ meristically from those downstream of the falls. The former have significantly more gillrakers (mean 21.7 compared with 21.1) and parr marks (15.1 and 13.5) but fewer pyloric caeca (26.0 and 28.2) and vertebrae (64.7 and 67.1) than the latter. Growth appears similar to that of char inhabiting more typical spring habitats.