Fig. 10. Instantaneous particle traces are released from (A) a rake of rectangular grid of points in a plane 0.75 cm away from the leading edge of the pectoral fin and parallel to it. Using the instantaneous velocity field, the positions of theses particles were obtained by integrating the velocity at these points until the length of these traces exceeded a specified length, or the particles ended on a solid boundary, or exited the computational domain. These particle traces are colored according to the magnitude of velocity (in cm s^-1) at that location. (B) Middle of the downstroke, t=1.064 s. (C) Beginning of the upstroke, t=1.1017 s.