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Genetic Trends in Wild Whirling Disease Resistant Rainbow Trout Populations
Genetic Trends in Wild Whirling Disease Resistant Rainbow Trout Populations

​​​​​​​​​​​​​​​​Led By

Dr. Eric R. Fetherman

Study Area

Colorado River and Gunnison River

Project Status


Research Objectives

  • Evaluate genetic changes over time in rainbow trout populations established using whirling disease resistant rainbow trout.

Project Description

Rainbow trout populations across the state have been re-established within the last decade using whirling disease resistant rainbow trout strains. Management changes from water to water, with different strains being stocked for different management purposes. Additionally, the size of fish stocked can differ among waters or years dependent upon management goals.

As these rainbow trout strains become established and start reproducing naturally, outcrossing and backcrossing can occur. Outcrossing can also occur in the hatchery as a result of maintaining crosses of wild and whirling disease resistant rainbow trout strains as opposed to the pure strains. Outcrossing and backcrossing can result in differential expression of the genes controlling for resistance to whirling disease through selection in both hatcheries and in the wild, and could result in loss of resistance over time.

This study is designed to look at the genetic composition of wild whirling disease resistant rainbow trout populations across years since they were established. Using stocking records to determine parental origin of wild fish, and collecting genetics from both the adult spawning population and age-0 fish naturally produced in the wild, researchers will be able to determine how different management strategies affect the genetics of these populations. Additionally, disease information collected from these same individuals will be used to determine if whirling disease resistant characteristics are changing or being maintained in these populations.

This study focuses primarily on the wild rainbow trout populations in the Colorado and Gunnison Rivers, although samples collected from other river systems will help elucidate trends statewide. This is a collaborative project between Colorado Parks and Wildlife, Colorado State University, and the University of California Davis.​