Fig. 8. Sum of the regressions for each individual vortex's circulation to determine how total circulation changes as flow moves down the body. Broken lines on each plot indicate the slope of the flow speed; they are only visual guides and are not fit to the data. (A) Total circulation magnitude along the body over the tail beat cycle, composed of the smoothed sum of the fitted circulations for each identified vortex. (B) Magnitude of circulation added per unit length by each position on the body over half of a tail beat cycle, estimated by taking the derivative of A with respect to position along the broken lines of flow speed. The zero contour is outlined in a thin solid black line, indicating that circulation is removed at certain times and places.