Effect of water velocity on swimming behavior of juvenile Megalobrama amblycephala

To investigate the swimming behavior of juvenile Megalobrama amblycephala, a tracking analysis device was designed to monitor behavior indicators including velocity (V), swimming distance (SD), turn angle (TA), distance to center-point (DC) and swimming track (ST) at different flow rates (0, 0.1, 0.2, 0.3 and 0.4 m/s) at 25℃. Results showed that indicator values all increased with increasing flow rate. Values of V, SD and TA showed no significant differences among the flow rates of 0, 0.1 and 0.2 m/s, respectively (P>0.05). However, they increased obviously at flow rates of 0.3 and 0.4 m/s (P<0.05), with no significant differences found between these two flow rates (P>0.05). The SD value did not change markedly according to flow rates (P>0.05), while ST showed complex patterns corresponding to increasing flow rate. A significant linear positive correlation occurred in free-swimming fish between V and SD, while a negative relationship was found between V and TA. No regular relationship was deduced between swimming speed and DC.