Fig. 7. Visualization of the dorsal fin wake during a slow turn at 0.5 L s^–1 by rainbow trout. The frontal-plane light sheet is at position 2 (Fig. 1A), and vectors overlying the body have been deleted; the dorsal fin is visible to the left and the adipose fin to the right. This image shows the dorsal fin soon after it has reached maximal excursion to the right of the body and has begun the return stroke toward the midline (indicated by the white arrow pointing to the left of the body). Unilateral dorsal fin abduction results in the well-developed vortex with clockwise rotation and the strong laterally directed jet. During the return stroke, the counterclockwise member of the vortex pair develops, the wake jet is strengthened and the fish's body yaws to the left. Free-stream velocity of 8.5 cm s^–1 has been subtracted from the vector field. Yellow scale arrow, 10 cm s^–1; white scale bar, 1 cm.