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Fig. 4. Measured values of peak fluid speed (cm s-1) and peak buccal
pressure (kPa) for largemouth bass (black upward triangles) and bluegill
sunfish (red squares), and the fluid speeds predicted from the model
(Muller et al., 1982) for
largemouth bass (black downward triangles) and bluegill sunfish (red circles).
As in previous plots, the absolute value of buccal pressure is shown. The
lines designated as `model' are based on values of peak fluid speed calculated
using the model (Muller et al.,
1982) for the pressures that we measured. This was done separately
for each species. See text for additional explanations. The slopes of the
linear regressions fit to the model output (0.51) are higher than the slopes
of the empirical data for largemouth bass (0.36) and bluegill sunfish (0.38),
and the values for fluid speed predicted by the model are well above the
measured values. Note that pressure explains more of the variation in fluid
speed for bluegill (r2=0.79; P<0.001) than
bass (r2=0.56; P<0.001). (A) Fluid speeds
where we measured them are shown, at a distance equal to 
peak gape
away from the mouth aperture; (B) fluid speeds at the mouth aperture. In order
to transform the measured values of fluid speed to values at the mouth
aperture, we multiplied the bass values by 4.6
(Higham et al., 2006) and the
bluegill values by 3.6 (Day et al.,
2005), based on empirical relationships of the drop in fluid speed
with distance from the mouth aperture. Note that the two species exhibit
different relationships between pressure and fluid speed for fluid speeds
measured at the mouth aperture, whereas the two species are similar for fluid
speeds measured at peak gape away from the mouth.
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