Fig. 5. Digitized silhouette and midlines of a trout (A) entraining and (B) Kármán gaiting around a 5 cm D-section cylinder, along with corresponding ventral view images, from top to bottom (100 ms apart). Flow is from left to right at 2.5 L s^–1, where L is total body length. Note that during entraining the body axis is tilted at an angle to the x axis. Midlines of entraining fish demonstrate the lack of axial undulation, in contrast to the large amplitude body undulations seen in Kármán gaiting fish.