Figure 3.

Determining cardiorespiratory thresholds for thermal performance using Doppler spectrographs. (A) Doppler spectrographs recorded at the acclimation temperature (11°C), Arrhenius breakpoint temperature (T_AB; 15°C) and arrhythmia temperature (T_Arr; 26°C) of a juvenile Atlantic salmon (S. salar). (B) Arrhenius breakpoint temperature (T_AB) analysis of maximum heart rate (ƒ_Hmax) for a juvenile Atlantic salmon exposed to an acute warming event following pharmacological stimulation of ƒ_Hmax. The natural log of maximum heart rate (ln (ƒ_Hmax)) was plotted against temperature, and the discontinuity in temperature-induced increases in ƒ_Hmax, which represents T_AB, was determined using a piecewise, two-segment linear regression. T_AB is denoted by *.