Fig. 4. Representative sequences of gape (black circles), volume (red squares), fluid speed in the earthbound frame of reference (green upward triangles), and the change in volume per unit time (dV/dt; blue downward triangles) for (A) largemouth bass and (B) bluegill sunfish. Positive values of fluid speed indicate that the water is flowing towards the fish's mouth. Note that the volume ingested by largemouth bass is substantially greater than the volume ingested by bluegill sunfish. Also note that maximum gape of largemouth bass is approximately twice that of bluegill. For this figure, we applied a smoothing spline with a smoothing factor of 1 or 2 to each of the variables using Igor Pro 5.01 (WaveMetrics Inc., Lake Oswego, OR, USA).