Metabolic rate and critical thermal maximum CTmax estimates for westslope cutthroat trout, Oncorhynchus clarkii lewisi

We measured metabolic rates of adult native westslope cutthroat trout and non-native rainbow trout and the critical thermal maximum of adult westslope cutthroat trout. The results will inform and parametrize models used in the recovery planning of westslope cutthroat trout. Global warming is changing the thermal habitat of cold-water freshwater fishes, which can lead to decreased fitness and survival and cause shifts in species distributions. The Alberta population of westslope cutthroat trout (Oncorhynchus clarkii lewisi) is listed as 'Threatened' under the Canadian Species at Risk Act. The major threats to the species are the alteration in habitat and water flow, competition and hybridization with non-native trout species and climate change. Here, we conducted (i) intermittent-flow respirometry experiments with adult native westslope cutthroat trout and non-native rainbow trout (Oncorhynchus mykiss) and (ii) critical thermal maximum experiments (CTmax) with adult westslope cutthroat trout to obtain valuable input data for species distribution models. For both species, standard metabolic rate (SMR) was lower at 10 degrees C compared to 15 degrees C and westslope cutthroat trout had higher SMR than rainbow trout. Although there were inter-specific differences in SMR, forced aerobic scope (using a standardized chase protocol) was different at 10 degrees C, but no significant differences were observed at 15 degrees C because of relative smaller differences in maximum metabolic rate between the species. CTmax of westslope cutthroat trout acclimated to 10 degrees C was 27.0 +/- 0.8 degrees C and agitation temperature was 25.2 +/- 1.0 degrees C. The results from this study will inform and parametrize cumulative effects assessments and bioenergetics habitat modelling for the recovery planning of the species.

Automated summary

This study measured the metabolic rates of native westslope cutthroat trout and non-native rainbow trout, as well as the critical thermal maximum of westslope cutthroat trout. The results will provide valuable input data for species distribution models and inform the recovery planning for westslope cutthroat trout. Global warming is a major threat to this species, as it is altering the thermal habitat of cold-water freshwater fishes.