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-emerged 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 exhibiting short hover durations exhibited long move durations, and vice versa. Our study supported the hypothesis that intermittent locomotion was associated with the perceptual challenges of detecting and capturing prey. When individuals switched between hovering and moving, they altered where they directed foraging attempts within the water column and, for benthic and midwater attempts, they experienced changes in the probability of capturing potential prey. Our study did not support alternative, energetic hypotheses suggesting that intermittent locomotion improves endurance or decreases energetic expenditures. A forced-swimming experiment in the field demonstrated that individual charr were easily capable of exercise periods 14 times longer than the move duration typically exhibited while foraging, and swimming speeds while moving were below the maximum sustainable speed reported for this species and life stage. In addition, video recordings revealed that swimming charr did not exhibit the burst-coast form of intermittent locomotion that can reduce the energetic cost of movement.