Fig. 2. Representative PIV measurements of the fluid field in front of the feeding fish at four times; opening (A), prey entering (B), peak gape (C), and closing (D) during the strike. Color contours represent the magnitudes of fluid speed and streamlines show the direction of velocity. The position of both the predator and prey are shown overlaid on the PIV measurement. Note that the region of significant fluid velocity induced by suction is constrained to a region in close proximity to the mouth and extends approximately equidistant in all directions from the mouth, and that the magnitude of speed and size of the affected region both increase during mouth opening and are maximum at peak gape. Measurements with a signal-to-noise ratio less than 2.0 are removed, but the more rigorous validation scheme that was applied to the extracted profiles has not been applied, resulting in some erroneous measurements near and within the mouth aperture in frames A and B.