Fig. 3. Rate of oxygen consumption (_O2) at 18 °C (blue plane and symbols) and 24 °C (green plane and symbols) as a function of both swimming speed and fish mass for all individuals studied. The maximum and minimum values of speed and mass at 18 and 24 °C were used to solve the multiple regression equations for _O2 (Table 2) for the four corners of each plane. At a given speed and mass, _O2 is significantly higher at 24 than at 18 °C, and the rate of increase in _O2 with speed is greater at 24 °C (ANCOVA, P<0.0001).