For most fish species, locomotion plays integral roles in the two fundamental phases of energy acquisition: foraging (the act of searching for suitable food items) and feeding (the physical act of food procurement). The vast majority of fishes actively swim to search for food. Some use sustained swimming to migrate to food resources or to track prey over long distances. Many intermittently swim shorter distances searching for food within much smaller spatial areas (e.g., O’Brien et al., 1990). Others use subtle, fine-tuned fin movements to hold station and remain cryptic as prey come to them. Once a food item is identified, locomotion is often essential for successful prey capture. The median or paired fins and/or the body axis may be used to position the body relative to the food item for effective suction feeding, during high acceleration strikes and highspeed chases (e.g., Keast and Webb, 1966; Blake, 1983; Webb, 1984a, c, 1986; Webb and de Buffrénil, 1990; Domenici, 2001; Guinet et al., 2007). Lastly, locomotion may also be used to rapidly turn, brake and reverse body movement after the food item is acquired. Thus, the phases of prey acquisition behavior, from foraging to feeding, require a range of locomotor behaviors and force the 172organism to encounter varying fluid mechanical constraints for steady- (i.e., constant swimming) and unsteady-state (accelerating, turning) swimming modes (Daniel, 1984; Webb, 1988). Phases of predation and the type of locomotion typically associated with them are diagrammed in Fig. 6.1.