Meeting Abstract
Tunas and their relatives have a number of behavioral and morphological adaptations to high-performance swimming. One morphological synapomorphy of this group is the presence of finlets – small fins on the dorsal and ventral surfaces of the body between the dorsal and anal fins and the tail. Although finlet kinematics and potential hydrodynamic functions have been studied, we lack an understanding of if and how they alter the hydrodynamics and performance of swimming in these fishes. We use morphological and kinematic data of finlets from Atlantic mackerel and yellowfin tuna to create and compare the performance of simple two-dimensional models of scombrid tails with flexible finlets, rigid finlets, and no finlets. Using these physical models, we quantify performance benefits of passively flexible finlets by measuring self-propelled speed, mechanical efficiency, and force traces during swimming. We also apply computational fluid dynamics to the biological kinematics of finlets in tuna and compare the performance of tuna-like models with and without finlets. Analysis of both physical models and vortex dynamics provides evidence of hydrodynamic functions for finlets during steady swimming.
