Lake trout ( Salvelinus namaycush ) is an important food fish in northern communities, inhabiting cool, well‐oxygenated water, but climate change is reducing available habitat, with extended summer stratification of lakes creating an upper thermal barrier (~15°C) and lower dissolved oxygen (DO) boundary (4–7 mg L −1 ). Together, these environmental factors can influence tolerance thresholds and climate change may lead to abiot...

The upper thermal tolerance of brook trout Salvelinus fontinalis was estimated using critical thermal maxima (CT max ) experiments on fish acclimated to temperatures that span the species' thermal range (5–25°C). The CT max increased with acclimation temperature but plateaued in fish acclimated to 20, 23 and 25°C. Plasma lactate was highest, and the hepato‐somatic index ( I H ) was lowest at 23 and 25°C, which suggests additio...