Fig. 2. Scaling of Suction Index (SI) and its underlying morphological components in bluegill, Lepomis macrochirus. (A) SI is a morphology-based index that describes the fish's potential to create suction pressure [Carroll et al., 2004; image modified from Collar and Wainwright (Collar and Wainwright, 2006)]. SI (arbitrary units) increases proportionately with the fish's length (B), due to the positive allometry of the lever ratio (C), the positive allometry of the cross-sectional area of the epaxial muscle (mm²) (D),and isometry of the buccal area. Buccal area is calculated based on morphological gape (mm) (E) and buccal length (mm) (F). Morphological gape and buccal length are also used, together with gape kinematics, to predict peak flow speed based on the Expanding Cone model (eqn 3; Fig. 3C). A_e, cross-sectional area of the epaxial muscle; L_in, in-lever arm, L_out, out-lever arm, B_area, buccal area. In the inset for each panel (B–F) the components of SI contributing to the dependent variable (y-axis) are colored red. Data are for N=11 fish (open circles=8 experimental fish; closed circles=3 other specimens).