Influence of Habitat Availability on Spawning Site Selection by Kokanees in Streams

Abstract

Abstract Spawning sites of kokanees Oncorhynchus nerka in two tributaries to Flaming Gorge Reservoir, Wyoming–Utah, were described. Water depth and current velocity at spawning sites in Sheep Creek (mean wetted width, 8.4 m) and the Green River (mean, 68 m), as well as available habitat in the reaches of the streams used for spawning, were measured in 1985. Modal water depths at redds differed between the two streams, whereas modal current velocities at redds were similar despite substantial differences in available habitat. The data indicate that habitat use curves illustrate kokanee spawning site distributions in a more realistic manner than habitat selection curves that incorporate both habitat use and habitat availability in their computation.