Meeting Abstract
Many fish are notable for their astonishing swimming abilities, and many of their behaviors such as finding food, migrating, or avoiding predators rely on their ability to swim effectively. As such, an understanding how swimming locomotion arises can help reveal evolutionary pressures leading to the diversity of body forms we see in fishes today, and further, can inspire designs for fast, efficient underwater vehicles. Yet, our ability to understand the nuances of the distributions of these forces and the mechanisms through which they are generated has been limited by the difficulty of measuring forces on a live, freely-swimming fish. Here, we use a recently developed, non-invasive, particle image velocimetry-based method technique to calculate pressure distributions on a bluegill sunfish (Lepomis macrochirus) swimming freely using body-caudal fin locomotion. From these pressure data, locomotor forces can be accurately estimated at high spatial and temporal resolution. We describe the distribution of forces and show that thrust and drag are produced in characteristic, separate regions of the body. By looking simultaneously at fish kinematics and the pressure and force distributions, we describe the mechanisms by which swimming forces are produced. In this way, we compare the contributions of low (suction) and high pressure to the thrust and drag acting on a carangiform swimmer, and contrast this with previous work on anguilliform swimming.
