9507197 The speed and maneuverability of fishes have long captured human imagination. Most research has been concerned with how fish swim at high speeds and accelerate at high rates, but as yet we have little understanding of the causes for differences between species. Maneuverability may provide the unifying explanation, yet there are virtually no studies on fish maneuverability, its effects on speed and acceleration, or how variability in fish body and fin form improves or restricts maneuverability. The purpose of the proposed research is to fill this gap. Maneuverability includes two components: the ability to turn in a small radius circle (turning radius) and the ability to turn at high rate (agility). Fish use different patterns, or gaits, of locomotion to swim at different speeds. Their primary gaits are routine swimming powered by the median and paired fins, cruising and sprinting with the body and tail fins, and fast start accelerations using the body and tail fins. Maneuverability differs between gaits, and experiments will be performed to measure maneuverability in each gait using mazes, circular raceways, and fast start trials. Maneuverability will be measured using frame-by-frame analysis of movie or video recordings. Three fish species varying in body shape and fin location will be studied. Measurements of maneuverability during feeding around obstacles and movement through mazes will determine whether how shape affects motor performance (maneuverability) and energy gain during median and paired fin swimming. During sprints, fish are expected to reduce speed to turn. This contrasts with current theory for fish, which may be based on sub-maximum performance levels. Analysis of fast-start maneuvers will test a unified model in which overall performance depends on speed, the timing of a turn and its radius. These variables determine the general pattern of the behavior, the specifics of linear acceleration and deceleration patterns and the final escape trajectory. The research will provide detailed measurements of maneuverability in various activities and a unified approach to intra- and inter-specific variation in swimming behavior. Because maneuverability may constrain habitat selection, the research should contribute to solving problems like the rehabilitation of aquatic habitat. Understanding the factors that limit speed and maneuverability will facilitate construction design that minimizes fish losses due to entrainment in industrial practices.