Meeting Abstract
Most fishes adopt different styles of locomotion depending on their swimming speed. To achieve their highest speeds they must transition from steady swimming to burst-and-coast swimming, where the body alternately accelerates and passively coasts. Despite the fact that burst-and-coast swimming is crucial for behaviors such as prey capture and predator evasion, the lack of a detailed kinematic characterization prevents a deeper understanding of the underlying mechanisms involved. We used high speed, high resolution video to record burst-and-coast kinematics of rainbow trout (Oncorhynchus mykiss, n=7 fish, body length L = 22.4±2.0 cm) swimming at different flow speeds. More than 100 burst and coast events were analyzed to calculate tail beat frequency, tail beat amplitude, duration of burst and coast phases as well as the initial and final velocities during burst phase. Remarkably, we found that bursting and coasting trout could reach swimming speeds up to 10 L s-1, which is twice their maximum speed during steady swimming. During bursting, tail beat frequency increased linearly with the average swimming speed (y=1.84x+1.81, R2=0.84, p<0.01), while tail beat amplitude remained constant (0.17±0.1 L). In addition, we found that the duration of burst-and-coast events shortened as average swimming speed increased, and the range of initial and final velocities of the burst phase was highly constrained (10% below and above the average swimming speed, respectively). Our results suggest that during burst and coast swimming frequency modulation is the primary mechanism to increase swimming speed.
