Meeting Abstract

3.2  Friday, Jan. 4  Why do fish have different shapes? A test using simple physical models FEILICH, K. L.*; LAUDER, G. V.; Harvard University, Cambridge, MA; Harvard University, Cambridge, MA kfeilich@fas.harvard.edu

Variation in fish tail and body morphology is one of the most frequently studied features in analyses of fish ecomorphology. There are myriad suggestions for why and how different caudal morphologies may be adaptive in light of fishes’ ecology, but none empirically demonstrate a mechanistic basis for performance enhancement. We sought to determine the physical consequences of two traits with purported adaptive significance: peduncle depth and the presence of a tail fork, on undulatory swimming performance. These two traits are often believed to be associated with tradeoffs in swimming economy and acceleration in both inter- and intraspecific comparisons. We attached simple flexible plastic models of different tail shapes as well as the caudal fins of dead fishes to a robotic motor controller and measured force, flow, and 3D kinematics to demonstrate how variation in shape and stiffness may actually translate into differences in the energetic costs, force production, and swimming speed. Future studies using models and live fishes in a controlled way will better inform ecomorphological comparisons, bridging the gap in the experimental literature between body shape and swimming performance.