WALKER, J.A.; WESTNEAT, M.W.; SANDBERG, W.C.; RAMAMURTI, R.; ROSENBERGER, L.: Kinematics, Dynamics, Energetics, Performance, and Ecomorphology of Rowing and Flapping Propulsion

A salient feature of fish locomotion is the wide diversity of both propulsors and the way these propulsors move and interact with the water to generate propulsive forces. What are the dynamic and energetic differences between these different swimming modes and how do these differences constrain fish ecology and evolution? We have investigated the highly variable kinematics, dynamics and energetics of pectoral fin, or labriform, propulsion. One conspicuous axis of the kinematic variation is the rowing-flapping axis. At one extreme of this axis, paddle-shaped fins row back and forth in a plane that is parallel to fish motion, while at the other extreme, wing-shaped fins flap up and down in a plane that is perpendicular to fish motion. Recent and ongoing studies in our labs confirm some traditionally held assumptions about rowing and flapping dynamics and energetics but reject others. We used a simulation experiment to compare thrust and efficiency between rowing and flapping fins. The results of the experiment suggested that fishes with a flapping stroke should have higher swimming endurance than fishes with a rowing stroke. This hypothesis was supported with a comparison of different labrid species whose fin motion varied along the rowing-flapping axis. These simulation and laboratory results are, in turn, supported by recent studies of fish position and behavior on coral reefs that suggest that flapping and its associated fin shape have been selected for increased cruising ability in high energy environments.