The critical swimming speed (U(crit), aerobic swimming performance) and endurance (anaerobic swimming performance) of juvenile southern catfish Silurus meridionalis Chen (9.8+/-0.1 cm body length and 8.09+/-0.17 g body mass, n=226) were investigated at 10, 15, 20, 25, and 30 degrees C. Both absolute U(crit) (cm s(-1)) and relative critical swimming speed (U(r), BL s(-1)) of juvenile southern catfish increased in the temperature zone from 10 to 25 degrees C (p<0.05) and plateaued between 25 and 30 degrees C. However, the relationship between endurance time (tested at 1.23, 1.59 and 1.79 U(r-max)) and temperature followed an approximate bell-shape curve as temperature rose (p<0.05). The optimum temperatures of maximal U(crit) (3.40 BL s(-1)) of juvenile southern catfish was 28.4 degrees C. But that of experimental fish's endurance which was tested at velocity of 1.59 and 1.79 U(r-max) was 23.2 degrees C. These results show that temperature has a significant effect on swimming performance in juvenile southern catfish.