STRATEGIES OF BURST-COAST SWIMMING BEHAVIOR OF JUVENILE SILVER CARP AT DIFFERENT FLOW VELOCITIES

At the water temperature of (18±1)℃, the current study investigated the strategies of burst-coast swimming behavior of juvenile Silver carps Hypophthalmichthys molitrix (at full length of 11.70±0.57 cm) such as swimming duration, percentage of turned-around, burst time, distance and speed in the burst-coast performance at different flow velocities (16.5, 22.0, 27.5, 33.0, 38.5, 44.0, 49.5 and 55.0 cm/s). Results showed that the average swimming duration of silver carps first decreased and then increased with the increasing flow velocity. The shortest duration time is 118.6min when fish swim at 33.0 cm/s. The maximum duration of swimming in each group was more than 200min. The percentage of turned-around quickly decreased with the increasing flow velocity, while no turned-around behavior occurred at the flow velocity ≥44.0 cm/s. The average burst time of burst-coast swimming of silver carp were positively associated with flow velocity (y=0.03x+2.64, R²=0.92, P<0.05). Average burst distances relative to the ground for each group were at the range of 30-45 cm without significant difference (P>0.05). However, the average absolute burst distances increased significantly with the increase of flow velocity (y=4.98x-5.63, R²=0.98, P<0.001). The average mean burst velocities relative to the ground and average maximum burst velocities relative to the ground had no significant difference (P>0.05), which were at the range of 9-12 cm/s and 12-16 cm/s, respectively. There was a positive linear relationship between average absolute burst velocity and flow velocity (absolute average mean burst speed:y=0.98x+10.74, R²=1.00, P<0.001. The absolute average maximum burst speed formulated by y=1.02x+13.75, R²=0.99, P<0.001). These data proved that silver carp took different burst-coast behavior strategies at different flow velocities.