Fig. 3. Kinematic patterns for the soft dorsal and adipose fins of trout oscillating in tandem during steady swimming at three speeds. The image at the top illustrates the points digitized from dorsal-view video (Fig. 1A, plane 2): red and blue symbols indicate the trailing edges of the dorsal and adipose fins, respectively, with body reference points at corresponding longitudinal positions represented by white symbols. At low swimming speed (0.5 L s^–1), the amplitude of dorsal fin oscillation exceeds the amplitude of body bending (A), while the excursion of the adipose fin closely tracks that of the body (B). With increasing speed (1–2 L s^–1) dorsal fin amplitude declines as body amplitude increases (C) until the dorsal fin's trailing edge and the body exhibit nearly identical excursion patterns (E). At higher speeds, the frequency and amplitude of adipose fin oscillation continue to match those of the body (D,F).