In order to evaluate the energy cost after acclimation to the different experimental salinities, energy expenditures were calculated by converting the measured physiological rates to energy equivalents. Energy lost through oxygen consumption (R) and excretion (U) was calculated by converting the physiological rates to energy equivalents using the following conversion factors: 1 mg O2 = 14.06 J (Gnaiger, 1983) and 1 mg NH4–N = 24.87 J (Elliot and Davison, 1975).