THE EFFECTS OF FOOD DEPRIVATION ON INDIVIDUAL VARIATION AND REPEATABILITY IN SWIMMING PERFORMANCE OF JUVENILE SOUTHERN CATFISH (SILURUS MERIDIONALIS CHEN)

In this study, we used the juvenile southern catfish (Silurus meridionalis Chen) as the experimental model to investigate effects of food deprivation on individual variation and repeatability of both aerobic and anaerobic swimming performance in carnivorous fish. The critical swimming speed (Ucrit), constant acceleration speed (Ucat), and the endurance of both the control group (n=28) and fasting group (n=29) were measured before and after fasting under (25 0.5)℃. Our results showed that the body mass, body length and condition factor of the fasting group decreased significantly by (15.100.86)%, (2.570.40)% and (7.941.59)% after the fasting treatment (P0.05), respectively. In the contrast, these morphological parameters of the control group did not change after the fasting treatment. In terms of swimming performance, the control group showed no difference in Ucat and endurance, but the Ucrit declined significantly by (6.632.25)% (P=0.031) after the fasting treatment. Unlike the control group, the fasting group showed remarkable decrease in Ucrit and Ucat by (26.002.76)% and (13.681.86)% (P0.001) respectively, without change in the endurance. The decreased proportion of the Ucrit was greatly larger than that of the Ucat (P0.001) in the fasting group. The coefficient of variation (CV) of the endurance, Ucrit and Ucat of the fasting group uniformly increased after the fasting treatment, whereas the CVs of the control group changed both positively and negatively. A significant positive correlation between Ucrit and Ucat of the S. meridionalis was observed in either control or fasting group, and two-week food deprivation did not affect this correlation. This implied that there was no potential trade-off between aerobic and anaerobic locomotion ability in individual southern catfish. The present study suggested that fasting profoundly decreased aerobic and anaerobic swimming performance in juvenile southern catfish, but increased the CV of their swimming performance. The correlation between aerobic and anaerobic swimming ability maintained stable during food deprivation. The physiological traits of anaerobic swimming may be relatively conservative in the environment compared to aerobic swimming. The shift in the large variation of individual performance may reflect divergent natural selection favoring alternative strategies for foraging and predation.