Field examination of perceptual and energetic bases for intermittent locomotion by recently-emerged Brook Charr in still-water pools

This study describes the intermittent locomotion exhibited by recently-emer ged brook charr (Salvelinus fontinalis) foraging in still-water pools along the banks of streams, and examines perceptual and energetic bases for it. Distributions of hover (pause) and move durations for brook charr foraging in the field were highly variable among individuals. On average, charr exhi biting short hover durations exhibited long move durations, and vice versa. Our study supported the hypothesis that intermittent locomotion was associ ated with the perceptual challenges of detecting and capturing prey. When i ndividuals switched between hovering and moving, they altered where they di rected foraging attempts within the water column and, for benthic and midwa ter attempts, they experienced changes in the probability of capturing pote ntial prey. Our study did not support alternative, energetic hypotheses sug gesting that intermittent locomotion improves endurance or decreases energe tic expenditures. A forced-swimming experiment in the field demonstrated th at individual charr were easily capable of exercise periods 14 times longer than the move duration typically exhibited while foraging, and swimming sp eeds while moving were below the maximum sustainable speed reported for thi s species and life stage. In addition, video recordings revealed that swimm ing charr did not exhibit the burst-coast form of intermittent locomotion t hat can reduce the energetic cost of movement.