Meeting Abstract
Archer fish (Toxotes microlepis), best known for their ability to spit jets of water at aerial prey, will also jump multiple body lengths out of the water for prey capture, especially in competitive foraging scenarios where kleptoparasitism is prevalent. Aiming prior to jumping or spitting occurs from a stationary position with the snout directly below the free surface. Rapid acceleration to a ballistic velocity sufficient for reaching the prey height occurs with only a body length to travel before the fish leaves the water completely and experiences a thousandfold drop in force producing ability. Simultaneous high-speed, three-dimensional measurements of fin kinematics and aerial body trajectories highlight multiple strategies for such spatially constrained acceleration. The fish performs an S-type acceleration maneuver, followed by additional caudal fin strokes with the motion envelope more confined to the submerged portion of the body. The pectoral and pelvic fins rapidly extend fins at jump onset, altering the added mass forces acting on the fish. Volumetric synthetic aperture particle image velocimetry (SAPIV) is used to provide time-resolved measurements of fluid wake development during a jump, including simultaneous quantification of contributions made by the pectoral, anal, and caudal fins to the wake kinetic energy. 3D fluid flow measurements also enable assessment of propulsive efficiency, which is crucial to understanding jumping’s role as an energetically viable hunting strategy for the fish.
