Critical Thermal Maxima for Young Salmonids

The critical thermal maxima LT50 (temperature giving 50% mortality) was determined in two laboratory experiments with 2–3 months old (0+) salmonids. These varied from 25.9°C for lake trout (Salvelinus namaycush) to 29.2°C for Atlantic salmon (Salmo salar). The critical thermal maxima for brook trout (Salvelinus fontinalis), brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) varied from 26.2 to 27.9°C in the two experiments. The fish were actively feeding at temperatures close to their respective maxima. Temperatures may be one factor affecting the competition between these species.