Mechanics of foraging success and optimal microhabitat selection in Alaskan Arctic grayling ( Thymallus arcticus )

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Authors: Bozeman, Bryan B., Grossman, Gary D.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2019
• Subjects: Aquatic Science; Ecology, Evolution, Behavior and Systematics; Arctic; Varden; Arctic grayling; Thymallus arcticus
• Online Access: http://dx.doi.org/10.1139/cjfas-2018-0115; http://www.nrcresearchpress.com/doi/full-xml/10.1139/cjfas-2018-0115; http://www.nrcresearchpress.com/doi/pdf/10.1139/cjfas-2018-0115

Most fishes residing in temperate streams in the Northern Hemisphere are drift-feeders. Despite this fact, little is known about the mechanisms of drift-feeding itself. We used Alaskan Arctic grayling (Thymallus arcticus), an abundant boreal drift-feeder, to examine the effects of water velocity on several aspects of drift-feeding behavior and test predictions of the Grossman et al. (2002) net energy intake model for microhabitat choice. Water velocity had a negative effect on prey capture, a positive effect on holding velocity, and little effect on reactive distance. We also found that dominance was a better predictor of prey capture success than size rank, although neither of these variables influenced holding velocity or reactive distance. The Grossman et al. (2002) model successfully predicted holding velocities of grayling in one Alaskan stream, but not another. Model failure might have occurred due to higher turbulence, increased predation, or interspecific competition with Dolly Varden (Salvelinus malma). These results help inform the study of habitat selection in drift-feeding fishes as well as management and conservation of Arctic grayling.