Meeting Abstract

P3.49  Saturday, Jan. 5  Locomotive function of the anal fin in boxfishes WOOLARD, A.M.*; BARTOL, I.K.; Old Dominion University; Old Dominion University awool006@odu.edu

Boxfishes (Teleostei: Ostraciidae) are remarkably stable and maneuverable rigid-bodied swimmers, relying predominantly on complex motions of their median and paired fins for propulsion over most of their speed range. Recent studies have shown that the carapace keels and contours are important for correction of pitching and yawing instabilities, but little is known about the stabilizing or even propulsive role of the anal fin, which is active in all but the fastest of swimming gaits. In this study, we examined the hydrodynamics of anal fin function in spotted boxfish Ostracion meleagris and smooth trunkfish Lactophrys triqueter during pitching, yawing, and rectilinear swimming using digital particle image velocimetry (DPIV). The experiments were conducted in a water tunnel using a 3-camera, motorized traverse system to track the boxfishes and record DPIV and kinematic data. Based on DPIV results, the anal fin was capable of producing forces of significant strength to override the self-correcting flows induced by the keeled carapace, allowing the boxfishes to maintain yaw when necessary. The anal fin also produced jets of varying angle, depending on swimming speed, to facilitate thrust production and/or aid the keel-induced flows in the correction of non-desirable yaw resulting from self-generated and external perturbations. During negative pitching, the anal fins were able to override or augment keel-induced flows much like that observed during yawing motions. These results suggest that interaction between passive vorticity generation by the carapace keels and active vorticity production by the fins is important for stability and maneuverability in boxfishes.