Fig. 4. Examples of each of the ten different vortices identified. All images have the original PIV image in the background, yellow vectors represent the flow field, and vorticity is shown as colored contours. In all panels, scale bars are 5 mm and scale vectors are 5 cm s^–1. The heads of vectors shorter than 3 cm s^–1 are retained to indicate direction. (A) Flow field at the posterior margin of the caudal fin, with the laser illuminating the upper and lower lobes of the fin. The tail is moving from left to right and has just formed the two tip vortices, labeled `caudal fin (upper)' and `caudal fin (lower)'. Weak remnants of the outer dorsal and anal fin vortices are still present, labeled `dorsal fin' and `anal fin'. The notch between the two lobes of the caudal fin also sheds vortices, labeled `caudal notch (upper)' and `caudal notch (lower)'. Every other vector is shown. (B) Flow field at the trailing edge of the dorsal and anal fins, with the laser illuminating the two fins and part of the caudal peduncle. The caudal fin blocks the view of some of the flow field. The fins are finishing motion from left to right, and the peduncle has just begun to move from right to left. Outer vortices from the dorsal and anal fins are fully developed (labeled `dorsal fin' and `anal fin'). The fins have also formed vortices on their inner edges, labeled `dorsal fin (inner edge)' and `anal fin (inner edge)'. Two vortices may have been shed from the peduncle (both labeled `peduncle?'), but it is difficult to be certain because of the shadow cast by the peduncle. (C–E) Insets showing details of the vector fields boxed in A and B. All vectors are shown in these panels.