Meeting Abstract

7.3  Thursday, Jan. 3  Stabilizing and maneuvering function of fish pelvic fins STANDEN, E.M.; Harvard University, Cambridge, MA standen@fas.harvard.edu

Fish appear to have a preferred swimming speed. For example salmonids tend to maximize their swimming performance at speeds of 1.2-1.5 body lengths per second swimming with a distinct body and caudal fin oscillation. At these speeds, paired fin function appears minimal, fins are held next to the body presumably to reduce drag. When fish swim below this preferred speed, however, paired fins oscillate away from the body suggesting a need for increased stabilization. In this study I examine the stabilization and maneuvering functions of paired pelvic fins, hypothesizing that pelvic fins act as a controllable keel providing stabilizing forces at speeds below a fish�s preferred gait. To date the kinematic or hydrodynamic function of the posterior paired pelvic fins has not been described. I use particle imaging velocimetry and high-speed cameras to visualize the wake structures and kinematics of the pelvic fins in brook trout (Salvelinus fontinalis). I use a horizontal light sheet to visualize the entire fish belly and describe how the pelvic fin wake interacts with the anal fin during swimming. I also use EMG techniques to assess the activation patterns of pelvic fin muscles. Trout actively oscillate their pelvic fins in phase with the tail beat cycle, one fin abducting while the contralateral fin adducts. The contralateral oscillation of the pelvic fins produces distinct lateral jets that appear to influence and contribute to body stabilization by balancing and altering the wake patterns of other fins.