GUIGAND, C.M.; TURINGAN, R.G.: Scaling of feeding kinematics and morphology of juvenile tarpon Megalops atlanticus.

Scaling of feeding kinematics of juvenile tarpon Megalops atlanticus, was investigated to explore the effects of size on feeding mechanics. Eleven tarpon (127-310 mm total lengths) were filmed at 500 frames per second using a high-speed video system while feeding on mosquitofish Gambusia affinis . After 20 feeding bouts were recorded, each fish was killed and the left lower jaw was dissected to measure the biomechanical properties associated with jaw opening and closing. Morphological and kinematic variables were regressed against total length to generate scaling relationships. The slopes of these regression lines were compared to the slopes of two modes of geometric similarity using a modified t-test. Morphological measurements scaled isometrically. Furthermore, the kinematics of prey capture changed throughout ontogeny. Our results indicated that fish size had an effect on the feeding kinematics of juvenile tarpon: as tarpon grew their feeding routine slowed down. The time to reach maximum displacement of cranial elements increased and approach, lunge and cranial rotation velocities decreased. There was an increase in time to reach maximum excursion with increasing fish size. It is hypothesized that changes in muscle contractile properties might ultimately slow the feeding event of tarpon as they grow. The changes in mechanical advantage of the lower jaw, if present would also have variable impact on feeding kinematics. The feeding kinematics of tarpon do scale with size consistent with predictions made for other fish and aquatic vertabrates.