Velocity, prey capture success, and microhabitat selection in arctic grayling (thymallus arcticus)
Bozeman, Bryan Benjamin
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Our knowledge of factors affecting microhabitat selection for drift feeding salmonids is incomplete. We quantified relationships between water velocity, fish size, days in captivity, and dominance (predictor variables) and prey capture success, holding velocity, and reactive distance (response variables) experimentally for three sets of fluvial Alaskan Arctic Grayling. Water velocity had a negative effect on prey capture success and a positive effect on holding velocity in all experiments. Holding velocity increased at a slower rate than capture velocity and plateaued at 30 cm/s at velocities of 30 cm/s and greater. Reactive distance displayed a weak (positive) or nonexistent relationship with velocity. Dominant fish captured more prey than subordinate fish, but had similar holding velocities and reactive distances. Holding velocity predictions from Grossman et al.’s (Grossman et al., 2002) foraging model (41.2 cm/s, 36.2 cm/s, 34.7 cm/s) were greater than Arctic Grayling holding velocities measured in Panguingue Creek, AK (95% CI: 20.7 – 27.9 cm/s).