Resting metabolic rate, critical swimming speed, and routine activity of the euryhaline cyprinodontid, Aphanius dispar, acclimated to a wide range of salinities.

Specimens of the euryhaline cyprinodontid fish, Aphanius dispar, collected in salt ponds, were acclimated to salinities of <1 (freshwater), 35 (seawater), 70, 105, and 140 ppt for 4 wk before measurement of oxygen consumption, critical swimming speed, and routine activity level. Oxygen consumption was similar in <1, 35, and 70 ppt (0.18+/-0.07, 0.17+/-0.06, and 0.16+/-0.04 mL h(-1) g(-1), respectively [mean+/-SD]) but decreased in 105 and 140 ppt (0. 12+/-0.02 and 0.09+/-0.2 mL h(-1) g(-1), respectively). Critical swimming speed and routine activity levels showed the same trend. These results suggest a general decrease in physiological function of A. dispar at extreme salinities.