Thermal Adaptation of Westslope Cutthroat Trout

Scientific Disciplines
Biological Sciences - Aquatic
westslope cutthroat trout
cutthroat trout
fishes of yellowstone national park
yellowstone cutthroat trout
Technology Center 4050 Bridger Canyon Road Bozeman Montana
Montana State University
Zale Montana Cooperative Fishery Research Unit Department Ecology Geological Survey
Steven T Kalinowski Department Ecology Montana State University
Montana Cooperative Fishery Research Unit
Tessa Andrews
westslope cutthroat
populations westslope cutthroat trout
Volume 16, No. 4

Thermal adaptation of westslope cutthroat trout
Daniel P. Drinan and Alexander V. Zale,  Montana Cooperative Fishery Research Unit, Department 
of Ecology and U.S. Geological Survey,  301 Lewis Hall, Montana State University, Bozeman, 
Montana 59717
Molly A. Webb, USDI Fish and Wildlife Service, Bozeman Fish Technology Center,  4050 Bridger 
Canyon Road, Bozeman, Montana 59715
Tessa Andrews, Mark L. Taper, and Steven T. Kalinowski, Department of Ecology, Montana State 
University, 310 Lewis Hall, Bozeman, Montana 59717
Populations of westslope cutthroat trout (Oncorhynchus clarkii lewisi), a State species of 
special concern, have declined throughout their native range. Genetic introgressions, mainly 
from rainbow trout (O. mykiss), but also from Yellowstone cutthroat trout (O. c. bouvieri), and 
habitat loss are believed to be the leading causes of this decline. Populations that remain are 
often small and isolated, thereby increasing their risk of inbreeding depression and extinction. 
Translocation projects may offer a solution by infusing new genetic material into populations 
and potentially increasing their probability of persistence. However, local adaptations must 

be considered when selecting a donor population. We investigated thermal adaptations of 
four wild populations of westslope cutthroat trout from the Missouri River drainage and one 
hatchery population from the Washoe Park Trout Hatchery, Anaconda, Montana. Two wild 
populations were deemed to be from warm streams and two from cold streams. Fish were 
spawned streamside and at the hatchery. The resulting embryos were placed in experimental 
systems at 8, 10, and 14 °C. Survival was monitored throughout incubation. Post-embryonic 
growth was measured 90 days after hatching. Relationships between population performance 
and natal stream thermal characteristics were examined for adaptive differences.