| Suction feeding fish draw prey into their mouth using a flow field they generate external to the head. This flow is generated by a rapid expansion of the fish's mouth, or buccal cavity. The characteristics of the flow field are likely influenced by a number of factors, including the forward swimming speed of the predator. While previous studies of suction feeding in fishes have involved both kinematics and modeling, direct measurements of water flow are rare. The goals of this dissertation are to (1) determine the effects of swimming speed on suction generation, (2) present a multidimensional perspective on suction feeding performance, and (3) determine the relationships between in vivo buccal pressure and induced fluid speed. I studied two members of Centrarchidae, the largemouth bass (Micropterus salmoides) and bluegill sunfish (Lepomis rnacrochirus). Digital particle image velocimetry (DPIV) and high-speed video were used to measure the flow in front of the mouth of fish from each species in conjunction with a vertical laser sheet positioned on the mid-sagittal plane of the fish. Surprisingly, swimming speed did not affect the maximum speed of water entering the mouth of bluegill. However, the shape of the ingested volume of water was altered by changes in swimming speed. In the multidimensional suction feeding performance space, bluegill are more accurate during a strike, generate higher fluid speeds and accelerations, but ingest a much smaller volume of water than largemouth bass. The small mouth and deep body of bluegill are likely adaptations for generating high amounts of force during suction feeding. The existing model of suction feeding fails to accurately predict fluid speed and buccal pressure from buccal expansion kinematics. This suggests that a more complex model of suction feeding is necessary, at least for centrarchid fishes. |
