Investigations into the Pygmy Whitefish in Northwest Montana
Bourret S, Deraleau J, Schnee M, Fried L. 2024. Investigations into the Pygmy Whitefish in Northwest Montana. Research Permit and Reporting System
The genus Prosopium contains six species of freshwater whitefish: Bear Lake Whitefish P. abyssicola, Bonneville Whitefish P. spilonotus, Bonneville Cisco P. gemmifer, Mountain Whitefish P. williamsoni, Pygmy Whitefish P. coulterii, and Round Whitefish P. cylindraceum. Of these, the former three are all endemic to Bear Lake on the Idaho-Utah border while Mountain, Pygmy, and Round Whitefish are all found throughout North America. The distribution of the Pygmy Whitefish is associated with glacial refugia (McPhail and Lindsey 1970) and they are primarily found below 100 feet in coldwater lakes (Sullivan and Mackay 2011; MNHP 2020). Pygmy Whitefish are found in the lakes of the Northern Rockies, western Washington, Lake Superior, several southern Alaska basins, the Canadian Arctic, and Ekityki Lake, Russia (Chereshnev and Skopets 1992; Hallock and Mongillo 1998). Such a distribution is likely the consequence of widespread migration during the repeated glaciations of the Pleistocene, approximately 2.6 M – 12,000 years ago (McPhail and Lindsey 1970). Indeed, Alaskan and Pacific (British Columbia, Washington, Idaho, and Montana) populations are highly genetically divergent, a grouping consistent with relict populations being associated with the Beringia and Cascadia glacial refugia (Witt et al. 2011). The first record of Pygmy Whitefish in Montana was made by Leonard Schultz- University of Washington- in tributaries of Lake McDonald, Glacier National Park (Schulz 1941) and then by George Weisel- University of Montana- from Bull Lake, in the Kootenai drainage (Weisel and Dillon 1954). Since then, 13 more populations have been identified in the state (Table 1). Of these populations, only those in Bull and Flathead Lakes have been examined in any depth; the morphology, reproductive age, and diet of Pygmy Whitefish in both lakes was well described in early investigations (Weisel and Dillon 1954; Hanzel 1970, 1972a, 1972b, 1974; Weisel et al. 1973).