Meeting Abstract
Fish live in a complex three-dimensional world and need to actively adapt their swimming behavior to a range of environments. The majority of fish swimming kinematics studies focus on two-dimensional properties related to the bending wave that passes from the head to tail. In our study, we characterize how fish bodies twist around their longitudinal axis as the bending wave passes down the body. We measured this movement, which we call ‘wobble’, in six species of elongate fishes (Anoplarchus insignis, Xiphister mucosus, Lumpenus sagitta, Pholis laeta, Apodichthys flavidus, and Ronquilus jordani) from three different ecologies (intertidal, nearshore, and subtidal) using custom video analysis software developed in Matlab and available at https://github.com/CDonatelli/Wobble. Wobble and bending are synchronized, with a phase shift between the wobble wave and the bending wave. In nearshore species, the tail wobbles the most but, in the subtidal and intertidal species, the head wobbles more than or the same as the tail. To determine if these differences in wobble were a passive movement related to differences in the mechanics of the bodies of the fishes, or were actively controlled, we used a material testing system to measure torsional stiffness at several points from behind the head to the tail. Although stiffness increases from head to tail in all six species, amount of wobble does not. These data suggest that wobble is not a passive property in all fishes, but can be actively controlled in at least some species, potentially playing an important role in the fish’s swimming behavior.
