Selection of Spawning Sites by Kokanees and Evaluation of Mitigative Spawning Channels in the Green River, Wyoming

Abstract

Selection of spawning sites by kokanees Oncorhynchus nerka was assessed over a 1‐km reach of the Green River in the tailwater of Fontenelle Dam, Wyoming, during 1990 and 1991. Within this reach three spawning channels were constructed in 1990 to mitigate losses of spawning habitat that were believed to have resulted from extensive deposition of gravel and rubble in 1986. The channels were built through an island of gravel and rubble in the river channel. Kokanees selected certain water depths, current velocities, and substrate sizes for spawning, but these three variables were not sufficient to fully account for spawning site selection. The distribution of recently deposited gravel and rubble, and the presence of shallow riffles that discouraged entry to a spawning channel also influenced spawning site selection. The spawning channels provided a substantial portion of the spawning habitat used by kokanees during 1990 and 1991, but high spring flows in 1991 substantially altered the morphology of the spawning channels and reduced their mitigative value.

Enhanced Incubation Success for Kokanee Spawning in Groundwater Upwelling Sites in a Small Idaho Stream

“…Although visual identification of upwelling sites is not possible, redd excavation in areas of unusually low water velocity (Ͻ20 cm/s) may indicate the presence of groundwater upwelling. Parsons and Hubert (1988) observed no kokanee spawning in sites with water velocity less than 24 cm/s, and Mullner and Hubert (1995) found no kokanee spawning where water velocity was less than 20 cm/s. In our study, water velocity at redds located in upwelling areas averaged 11.5 cm/s.…”

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“…Oncorhynchus masou masou Webster 1962; Klassen & Northcote 1988;Mullner & Hubert 1995;Avery 1996;House 1996;Kondolf et al 1996 Hayes 1987Roberts & White 1992Sorensen et al 1995Fukushima et al 1998Taniguchi et al 2000Yamamoto et al 2004Kubota et al 2007Kikko et al 2008…”