Cold tolerance performance of westslope cutthroat trout (Oncorhynchus clarkii lewisi) and rainbow trout (Oncorhynchus mykiss) and its potential role in influencing interspecific hybridization

• Published in: Canadian journal of zoology Vol. 92; no. 9; pp. 777 - 784
• Main Authors: Yau, M.M., Taylor, E.B.
• Format: Journal Article
• Language: English
• Published: Ottawa NRC Research Press 01.09.2014; Canadian Science Publishing NRC Research Press
• Subjects: Acclimatization; Cold; Cold tolerance; critical thermal minimum; Fish populations; Habitats; hybridation; Hybridization; Hybrids; Low temperature; Oncorhynchus; Oncorhynchus clarkii lewisi; Oncorhynchus mykiss; rainbow trout; Salmon; Spatial distribution; température de l’eau; température minimum critique; Trout; truite arc-en-ciel; truite fardée de Yellowstone; Water temperature; westslope cutthroat trout; Zoology
• ISSN: 0008-4301; 1480-3283; 1480-3283; 0008-4301
• DOI: 10.1139/cjz-2014-0047

Hybridization between rainbow trout (Oncorhynchus mykiss (Walbaum, 1792)) and westslope cutthroat trout (Oncorhynchus clarkii lewisi (Girard, 1856)) occurs commonly when rainbow trout are introduced into the range of westslope cutthroat trout. Typically, hybridization is most common in warmer, lower elevation habitats, but much less common in colder, higher elevation habitats. We assessed the tolerance to cold water temperature (i.e., critical thermal minimum, CTMin) in juvenile rainbow trout and westslope cutthroat trout to test the hypothesis that westslope cutthroat trout better tolerate low water temperature, which may explain the lower prevalence of rainbow trout and interspecific hybrids in higher elevation, cold-water habitats (i.e., the “elevation refuge hypothesis”). All fish had significantly lower CTMin values (i.e., were better able to tolerate low temperatures) when they were acclimated to 15 °C (mean CTMin = 1.37 °C) versus 18 °C (mean CTMin = 1.91 °C; p < 0.001). Westslope cutthroat trout tended to have lower CTMin than rainbow trout from two populations, second–generation (F 2 ) hybrids between two rainbow trout populations, and backcrossed rainbow trout at 15 °C (cross type × acclimation temperature interaction; p = 0.018). Differential adaptation to cold water temperatures may play a role in influencing the spatial distribution of hybridization between sympatric species of trout.