Meeting Abstract
Energetic efficiency has long been considered an important feature of routine animal behavior. In fluid environments, fish swim using body undulations to navigate and propel themselves forward, but direct measurement of work done by the body on the fluid has proven challenging. Moreover, fish often rely on unsteady maneuvers during tasks like navigation, feeding or predator evasion. Here we investigate spontaneous turns in zebrafish using a modified Particle Image Velocimetry (PIV) technique. The method is inspired by previous work on micro scale PIV and does not require a laser to record the movements of fluid particles in a specific 2D plane, but makes use of a narrow depth-of-field instead. We combine the obtained flow field measurements with pressure computations to estimate the interaction forces and the mechanical work done between the turning fish body and the fluid. Our results show that the majority of mechanical work is done by the body on the fluid and that energy is transferred to the water in two bursts. Our method allows quantification of the hydrodynamic cost of a turn and additionally provides information about how much each segment along the anterio-posterior body axis contributes to the energy transfer to the fluid. This method provides a rigorous way to quantify hydrodynamic mechanisms of fish swimming, and we expect that it could be valuable for future analysis of hydrodynamics in fish schools.
