Figure 1.
The relationship between aerobic scope (black line), maximum heart rate (fHmax; grey line), and temperature in Pacific salmon (Oncorhynchus spp.). Shown are the optimum temperature (Topt) and upper critical temperature (Tcrit) for aerobic scope, as well as the Arrhenius break temperature (TAB) and arrhythmic temperature (Tarr) of fHmax. The solid vertical line represents Topt, and the dashed lines indicate the optimum temperature range in which aerobic scope is ≥90% of that at Topt. Also shown are the temperature sensitivities (Q10) of aerobic scope (black) and fHmax (grey). A Q10 ≥ 2 represents an exponential increase with temperature. When fHmax becomes limited with increasing temperature (i.e. at TAB), there is a corresponding limitation in aerobic scope that ultimately sets Topt. Similarly, when high temperatures induce cardiac arrhythmia (Tarr), the capacity for aerobic activity is highly reduced, thus corresponding with Tcrit [16,26].