Changing environmental conditions may affect the swimming performance of fish by affecting energy sources through changes in temperature and concentration of dissolved oxygen (DO). It has become increasingly important to investigate the effect of temperature and DO on the swimming performance of fish species as hypoxia in aquatic environments worldwide is increasing due to the effects of anthropogenic global warming. To test how different swimming modes respond to thermal and DO changes, 3 measures of swimming performance were tested: critical swimming speed (U crit ), constant acceleration speed (U cat ), and maximum speed during a fast-start (U fast ). The changes in these 3 aspects of swimming performance in juvenile crucian carp Carassius carassius were quantified at 2 different temperatures (10 and 20°C) and 3 different DO concentrations (2.5, 5, and 9 mg l −1 ). U cat was ca. 110 to 156% of U crit , whereas U fast was ca. 394 to 472% of U crit , depending on the experimental conditions. Temperature had a significant effect on all 3 measures of swimming performance, whereas DO had significant effects only on U cat and U crit (U crit but not U cat decreased in the 2.5 mg l −1 DO group). The active metabolic rate (MO 2active ) under the different experimental conditions suggested that the decrease in U crit at a lower temperature and DO level could be partially explained by a decrease in oxygen uptake capacity. These results indicate that all 3 swimming measurements should be used when addressing how temperature affects swimming performance.

To investigate the effects of starvation and acclimation temperature on the escape ability of juvenile rose bitterling (Rhodeus ocellatus), we measured the fast-start escape and constant acceleration swimming performance of fish fasted for 0 (control), 1 and 2 weeks and half-lethal periods (6 or 4 weeks) at two temperatures (15 and 25 °C). Fish acclimated at a high temperature exhibited shorter response latency (R), higher maximum linear velocity (V max) and longer escape distance during escape movement (D 120ms) than those at the low temperature. Starvation resulted in a significant decrease in V max and D 120ms at either low or high temperature and a significant increase in R at only the high temperature in the half-lethal period groups (P < 0.05). The relationship between V max (Y, m s(-1)) and starvation time (X, week) was Y 15 = -0.062X + 1.568 (r = -0.665, n = 36, P < 0.001) at low temperature and Y 25 = -0.091X + 1.755 (r = -0.391, n = 40, P = 0.013) at high temperature. The relationship between U cat (Y, cm s(-1)) and starvation time (X, week) was Y 15 = -1.649X + 55.418 (r = -0.398, n = 34, P = 0.020) at low temperature and Y 25 = -4.917X + 62.916 (r = -0.793, n = 33, P < 0.001) at high temperature. The slopes of equations showed a significant difference between low and high temperature (F 1,63 = 9.688, P = 0.003), which may be due to the different energy substrate utilization when faced with food deprivation at different temperatures.