Temperature is one of the most important abiotic factors regulating development and biological processes in ectotherms. By 2050, climate change may result in temperature increases of 2.1-3.4°C in Manitoba, Canada. Lake sturgeon, Acipenser fulvescens, from both northern and southern populations in Manitoba were acclimated to 16, 20 and 24°C for 30 days, after which critical thermal maximum (CT_max) trials were conducted to investigate their thermal plasticity. We also examined the effects of temperature on morphological and physiological indices. Acclimation temperature significantly influenced the CT_max, body mass, hepatosomatic index, metabolic rate and the mRNA expression of transcripts involved in the cellular response to heat shock and hypoxia (HSP70, HSP90a, HSP90b, HIF-1α) in the gill of lake sturgeon. Population significantly affected the above phenotypes, as well as the mRNA expression of Na⁺/K⁺ ATPase-α1 and the hepatic glutathione peroxidase enzyme activity. The southern population had an average CT_max that was 0.71 and 0.45°C higher than the northern population at 20 and 24°C, respectively. Immediately following CT_max trials, mRNA expression of HSP90a and HIF-1α was positively correlated with individual CT_max of lake sturgeon across acclimation treatments and populations (r = 0.7, r = 0.62, respectively; P < 0.0001). Lake sturgeon acclimated to 20 and 24°C had decreased hepatosomatic indices (93 and 244% reduction, respectively; P < 0.0001) and metabolic suppression (27.7 and 42.1% reduction, respectively; P < 0.05) when compared to sturgeon acclimated to 16°C, regardless of population. Glutathione peroxidase activity and mRNA expression Na⁺/K⁺ ATPase-α1 were elevated in the northern relative to the southern population. Acclimation to 24°C also induced mortality in both populations when compared to sturgeon acclimated to 16 and 20°C. Thus, increased temperatures have wide-ranging population-specific physiological consequences for lake sturgeon across biological levels of organization.

#	Concept	H-Index	Publications	Citations
1	Biology	1	1	16
2	Metabolism	1	1	16
3	Nutrition	1	1	16
4	Physiology	1	1	16
5	Animal Nutrition	1	1	16

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