Fig. 2. Vector plots of particle motions in the vertical plane recorded 80 ms (top), 200 ms (middle) and 440 ms (bottom) after valve opening. Vector plots are based on (A) individual and (B) averaged trials (n=9). Arrows indicate the direction and velocity of particle motions. Note that the averaged plots are similar to the plots based on individual trials, i.e. that the vortex stimulus was reproducible from trial to trial. Scale vector, 12.5 cm s^-1. In this figure, as well as in Figs 7, 8, 9, 11, 12, the fish schematic indicates the size, location and orientation of the fish relative to the vector plots.