HUSKEY, S.H.*; WAINWRIGHT, P.C.; TURINGAN, R.G.; Western Kentucky University; University of California, Davis; Florida Institute of Technology: Scaling snook suction: effects of body size on feeding performance

Size can enable or constrain the ability of an animal to function and exploit its environment, and many vertebrates go through a significant change in body size during ontogeny. Common snook, Centropomus undecimalis, grow from 0.5 cm at hatching to 140 cm as adults. Our goal in this study was to determine how suction feeding performance, as measured by peak suction pressure amplitude, scales with body size in this species. We reasoned by analogy to vessel mechanics that suction pressure can be thought of as the force of buccal cavity expansion per unit of the projected area of the buccal cavity. Thus, we predicted that suction pressure would scale as the combination of buccal expansion force divided by buccal cavity projected area. Expansion force input was estimated as physiological cross-sectional area of the sternohyoideus muscle and buccal projected area from dimensions of silicon casts of snook oral cavities. Data were collected on 33 fish ranging from 36 mm to 770 mm SL. Sternohyoideus PCSA scaled to snook length with an exponent of 1.99 and buccal area scaled with an exponent of 2.01. Thus we predicted that peak pressure amplitude would not change with increasing snook size. Peak suction pressure amplitude was then measured with Millar pressure transducers in 12 snook ranging from 94 mm to 314 mm. We fed snook highly elusive penaeid shrimp to elicit maximum effort strikes. Average peak pressure amplitude across the twelve snook was 18.9 kPa below ambient, however there was no significant effect of snook size on peak pressure, confirming our prediction from the morphology. This result confirms other recent data in suggesting that the capacity to generate suction pressure does not change during ontogeny of fish species that show isometric growth.