Effect Of Temperature On Swimming Ability And Resting Metabolic Rate In Juvenile Southern Catfish (Silurus Meridionalis Chen)

Southern catfish (Silurus meridionalis Chen) is a warmwater, sit-and-wait foraging fish and spawns in early spring. Three series of experiments and the other one in juvenile southern catfish were conducted at five temperatures (10, 15, 20, 25, 30±0.5℃) and acute temperature exposure(20℃→10℃and 20℃→30℃), respectively. The effects of acclimated temperatures on critical swimming speed, endurance and the excess post-exercise oxygen consumption were conducted in juvenile southern catfish. The other effect of acute temperature change on critical swimming speed and resting metabolic rate was conducted in juvenile southern catfish.The results as follow:1. The absolute critical swimming speeds and relative critical swimming speeds of juvenile southern catfish at five temperatures were 16.39±0.71, 22.62±0.49, 30.68±0.40, 32.59±0.57, 33.13±1.17 cm/s and 1.83±0.09, 2.49±0.05, 2.88±0.06, 3.32±0.06, 3.37±0.09 BL/s, respectively. The relative critical swimming speed (Ur) showed a'bell-shape'increase course with enhanced temperature (T). The relationship could be described as: (N=71,R~2=0.780,P<0.001)2. Under five experimental temperatures (10, 15, 20, 25, 30±0.5℃), as to 4BL/s, the exercise duration of juvenile southern catfish were 44.4±5.3, 74.4±7.7, 143.6±15.2, 220±16.6 and 64.6±7.4 s, respectively. As to 6BL/s, the exercise duration of juvenile southern catfish were 22.4±2.9, 26.9±2.1, 53.6±4.9, 54.7±4.6 and 40.6±3.0 s, respectively. As to 8BL/s, the exercise duration of juvenile southern catfish were 9.8±1.4, 20.0±2.2, 44.9±3.7, 47.9±5.4 and 28.6±4.1 s, respectively. The exercise duration of juvenile southern catfish show a'bell-shape'increase course with increased temperatures.3. The resting metabolic rate (RMR) of juvenile southern catfish at different temperatures were 18.30±1.21, 23.93±1.03, 36.33±2.08, 51.43±3.66 and 45.14±2.56 mg O2/kg·h. With the increase of acclimated temperature, the resting metabolic rate of juvenile southern catfish showed an increased transformed character.4. After the exhaustive exercise, the peak oxygen consumption rate at five temperature treatments were 77.75±10.17, 95.44±8.51, 191.68±11.70, 180.63±10.29, and 164.18±8.82 mg O2/kg·h, respectively. The oxygen consumption rate finally fell down to the stable VO2 post-exercise. The factorial metabolic scopes of juvenile southern catfish at five different temperatures were 4.59±0.63, 4.59±0.43, 5.51±0.57, 3.76±0.24 and 3.95±0.15, respectively. The excess post-exercise oxygen consumption of juvenile southern catfish at five different temperatures were 48.60±7.15, 63.01±7.78, 173.29±23.26, 129.88±21.07 and 115.62±17.23 mgO2, respectively.5. Both the acute cold exposure and the acute heat exposure have not influenced on critical swimming speed of juvenile southern catfish (P>0.05).6. According to the acute cold treatment, the resting metabolic rate of juvenile southern catfish was declined to the relative steady metabolic level in a short time. The Q10 of RMR were 4.39 and 5.96 after cold exposure at 1h and 8h, respectively. As to the acute heat treatment, the resting metabolic rate of juvenile southern catfish was increased to the peak of oxygen consumption rate, and then recovered to the relative stable metabolic level. The Q10 of RMR were 2.81 and 2.45 after heat exposure at 1h and 8h, respectively.The indications in this study were as follows:1. According to the regression equation, the optimum swimming temperature of juvenile southern catfish is 28.4℃. This temperature is higher than optimum hatching temperature (18℃) of juvenile southern catfish, but it is lower than the optimum feeding temperature (29.15℃) and the optimum growing temperature (≥30℃). Some functions or life activities of fish may be possess different optimum temperatures.2. With determined the resting metabolic rate and critical swimming speed of juvenile southern catfish in acute exposure experiment. The stress extent to acute cold exposure in juvenile southern catfish was much higher than acute heat treatment. But acute exposure has not influenced on critical swimming speed of juvenile southern catfish. In addition, the endurance scopes of juvenile southern catfish at five temperatures show a shrinked trend with increased velocity. The swimming ability of juvenile southern catfish may be possess the lower dependence on temperature or lower thermal sensitivity. This property is well according with the sit-and-wait forging strategy of juvenile southern catfish.3. The critical swimming speed and excess post-exercise oxygen consumption of juvenile southern catfish show an increased course with increased temperature. The improvement of aerobic and anaerobic locomotive ability in juvenile southern catfish may be due to the increasing temperature. This adapted character caused by temperature might be the evolutionary results that fishes have been undergone a long time evolution in the nature.