Date of Award:

5-1996

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Wildland Resources

Department name when degree awarded

Aquatic Ecology

Committee Chair(s)

Chris Luecke

Committee

Chris Luecke

Committee

Charles P. Hawkins

Committee

Paul Wolf

Abstract

I investigated the relative abundance, spatial distributions, return to the creel, and growth rates of two genetic stocks of kokanee salmon, Oncorhynchus nerka, in Flaming Gorge Reservoir, Utah-Wyoming. The two genetic stocks consist of fish from the two major spawning populations of kokanee in the reservoir. One population, Shore Spawners, spawns along the eastern shoreline of the Open Hills area of the reservoir. The other population, Sheep Creek, spawns in Sheep Creek, a tributary located in the Canyon area of the reservoir.

Mitochondrial DNA of kokanee from each population was analyzed to determine haplotype differences between stocks. These haplotype differences were then used to determine the natal population of kokanee captured throughout the reservoir. Shore Spawner kokanee were more abundant relative to Sheep Creek kokanee both in the reservoir (93% to 7%) and in return to the creel (93% to 7%). Individuals from the two populations were not, however, distributed differently during the summer of 1995.

Midwater trawls conducted during August 1995 and 1996 showed that age-0 kokanee in the less productive Canyon area were significantly smaller than their counterparts in more productive reservoir areas. Measurements of adult kokanee returning to spawning areas in 1995 showed that spawning Sheep Creek kokanee were significantly smaller than their Shore Spawner counterparts. A common garden net pen experiment conducted on age-0 kokanee during the spring of 1996 showed a significant effect of genetic stock on Flaming Gorge kokanee growth. Both genetic stocks grew faster in the more productive areas of the reservoir, but Shore Spawner kokanee grew faster than Sheep Creek kokanee in seven of nine net pens. Potential physiological, behavioral, and life history differences between the genetic stocks that could explain these growth differences are discussed.

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