Mechanical efficiency of fish thrust induced by tail beating: comparison between kinetic energy and metabolic energy

Abstract

There are few studies that compare thrust power P_T induced by tail beating with net metabolic power P_net obtained from oxygen consumption and mechanical efficiency η (= P_T P_net ^-1) of fish thrust. In this study, P_T and P_net were obtained using two species of chub mackerel and Japanese dace, and η was calculated by comparing kinetic energy and metabolic energy. P_T was calculated by multiplying swimming speed V_swim and thrust force T obtained using two calculation methods, the Milne-Thomson principle and Kutta-Joukowski theorem. Comparing each value, η showed a certain ratio irrespective of fish species and swimming speed. Linear approximation resulted in P_T = 0.21 P_net for Milne-Thomson and P_T = 0.44 P_net for Kutta-Joukowski.