MCCAY, M.G.*; WAINWRIGHT, P.C.; DWYER, H.A.; CHEER, A.Y.; Univ. of California, Davis; Univ. of California, Davis; Univ. of California, Davis; Univ. of California, Davis: New Insights Into Suction Feeding from a Computational Fluid Dynamic Model

Suction feeding is the most commonly used mechanism of prey capture in fishes and other aquatic vertebrates, but little is known about the temporal or spatial patterns of water flow generated outside the fish’s head during suction feeding or how this flow influences prey capture performance. Using computational fluid dynamics techniques, we developed a three-dimensional computer model of suction feeding that we used to explore (1) the spatial distribution of flow velocity in front of the mouth, (2) the nature of the bow wave that is created in front of a forward swimming predator, and (3) the relative importance of drag and acceleration reaction in generating the forces that prey experience as a result of these flows. The velocity of water toward the mouth of a suction feeding fish diminishes greatly within a very short distance from the mouth of the fish, approximately proportional to the inverse of distance to the third power. This distance increased by only modest amounts when the fish greatly increased the suction velocity at its mouth opening. Forward body movement creates water movement away from the mouth of the fish (a bow wave) that must be overcome by suction in order to yield a net movement of water toward the mouth of the fish. We propose a new function for jaw protrusion: it ameliorates this effect of the bow wave on prey capture by moving the mouth opening (the suction source) out of the influence of the bow wave. During suction feeding, acceleration reaction force may dominate the total forces exerted on prey (depending on flow conditions and the size of the prey), suggesting that both water velocity and acceleration are important determinants of suction feeding performance.