Scaling of Suction flows in Bluegill

A major goal in organismal biology is to understand how form and function relate to one another, and the scaling of organismal performance has been instrumental in understanding the mechanistic links between the changes in form, function and ecology that occur as organisms grow. In this study, we used digital Particle Imaging Velocity (dPIV) to investigate the scaling of suction-induced flow speed and acceleration in the bluegill sunfish, a high performance suction feeding fish. We use a wide range of body sizes, from young-of-year fish to large adults and measure the spatial and temporal patterns of flows in front of their mouths. Our results show that as bluegill grow, the magnitude of peak flow speed they can produce increases, and the effective suction distance increases. Importantly, the observed scaling relationships between standard length and peak flow speed conformed to expectations derived from two biomechanical models (the Suction Index Model and the Expanding Cone model), indicating that the observed scaling depends on the scaling of underlying cranial morphology.