Burst-and-coast swimming needs to be optimized to outperform continuous swimming

Many fish species employ an intermittent swim pattern, also known as the burst-and-coast swim pattern, characterized by a period of body undulation followed by a straight glide. The burst-and-coast swim pattern is presumed as a strategy to increase energy efficiency in swimming, but its quantifiable analysis proves more challenging than continuous swimming due to the involvement of additional kinematic parameters. In this study, we employ both experimental and computational approach to systematically examine the correlation between burst-and-coast gait parameter and swimming performance, alongside the role of burst-and-coast swim in energy conservation, using the red-nose tetra fish as our model species which performs body and caudal fin (BCF) propulsion.

In our experimental aspect, the fish were induced to swim in a flume at prescribed speeds, with video recordings used to monitor variations in their gait as imposed flow velocities altered. The results show how fish modulates their burst-and-coast gait parameters as swimming velocity changes, and that the burst-and-coast gait change very likely optimize the swimming energetic performance.

In the computational aspect, we established a two-stage protocol. First, we simulated a series of burst-and-coast swim cases with a range of amplitudes and frequencies for the fish undulations. Then, segments from this simulation database were selected, cut and amalgamated to assemble any arbitrary burst-and-coast swimming gait. This approach facilitated a comprehensive comparison between burst-and-coast and continuous swimming. Our findings suggest that when adequately optimized, burst-and-coast swimming can consume less energy than continuous swimming. However, the effectiveness of burst-and-coast swimming strategy can decline drastically if not sufficiently fine-tuned.