Meeting Abstract

40.3  Saturday, Jan. 5  Computational model of aquatic feeding: Scaling of suction feeding dynamics from larval to adult fish YANIV, S; ELAD, D; HOLZMAN, R*; Tel Aviv University; Tel Aviv University; Tel Aviv University

To capture prey, larval fishes swim towards their target while rapidly opening their mouth to generate a flow of water external to the mouth. This feeding mode, termed “suction feeding”, is thought to be the universal feeding mode in larval fishes. The suction flow is key to feeding success, because it draws the prey into the predator’s mouth, countering possible escape response of the prey. Because of the difficulties inherent in making direct measurements and observations on small animals such as larval fishes, very little is known about these flows, how they translate to prey capture, and whether those flows change during early development. In this study, we used a Computational Fluid Dynamics model (CFD) to elucidate the flow dynamics inside and outside the mouth, from the scale of first feeding larvae to adult fish. Our simulations reveal that size has strong effects on the patterns of flow inside and outside the mouth. Peak flow speed and Reynolds numbers increased with increasing mouth size. The radial symmetry that characterises suction flows in adult fishes dissipated as mouth length decreased. In adult fish, flow decays rapidly outside the mouth, and suction flows have a negligible effect on particles movement at a distance of ~2 mouth widths. However in larval fish flow decayed much slower, and significant flows were observed at a distance of ~5 mouth widths. While invicid models are generally suitable to describe the flow in large mouth sizes, they fail at the size range that characterizes larval fish. The different flow regime in larval fish likely changes larval feeding performance, including their ability to exert forces on the prey, and lead to size-related changes in feeding efficiencies.