Meeting Abstract
Fish swim by passing a wave of motion from their heads, through the body, to the tail which produces thrust. In addition to the yaw motion of the tail, some twisting also occurs about the long axis of the body. This twisting motion, or wobble, is especially prominent in elongate fishes. Wobble can be seen passing down the fish’s body with the wave of motion in a dorsal view of the fish swimming. To measure wobble, we collected video data from six species of elongate fishes, Anoplarchus insignis, Xiphister mucosus, Lumpenus sagitta, Pholis laeta, Apodichthys flavidus, and Ronquilus jordani, using automated video analysis software developed in Matlab. We measured swimming speed, wave speed, tail beat frequency, lateral amplitude, and wobble amplitude. From the video data, we can see that the A. flavidus and P. laeta wobble the most, while R. jordani wobbles the least. We also used a material testing system (MTS) to measure torsional stiffness at several points along the length of the fish’s body. As we expected, stiffness increased as number of vertebrae decreases for 5 of the 6 species. A. insignis appears to be the least stiff species, though its vertebral count is the second highest. We will present results on how the torsional stiffness of the body and the number of vertebrae correlates with the amount of wobble.
