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Fan Creek Westslope Cutthroat Trout Restoration Project
Note: The Fan Creek project has been replaced by the Eradication and Exclusion project (2004-2005).

Dates: 2003-2004

Project Summary:
Click here for an enlarged photo
North Fork of Fan Creek contains a genetically pure population of westslope cutthroat trout .

The Aquatic Resources Center, Yellowstone National Park, has been working to restore westslope cutthroat trout to headwater tributaries of Yellowstone National Park in the upper Missouri River drainage. As part of this effort, Aquatic Resources Center staff collected genetic samples from putative westslope cutthroat trout in streams of the Gallatin River and Madison River drainages in the northwest region of Yellowstone National Park. Of all the streams sampled, only the North Fork of Fan Creek was found to contain a genetically pure population. A telemetry study conducted by the Montana Cooperative Fishery Research Unit, in collaboration with the Aquatic Resources Center, characterized seasonal movements of the genetically pure westslope cutthroat trout in the North Fork of Fan Creek and compared these movements to nearby hybridized populations in the mainstem of Fan Creek. No evidence was found to suggest that hybrids entered the North Fork of Fan Creek or the upper portions of the mainstem. Movements of most westslope cutthroat trout tagged in the North Fork were limited. Westslope cutthroat trout tagged in the upper mainstem either made short spawning migrations upstream within the mainstem or made longer migrations to the North Fork. Overall these findings suggested that spatial reproductive isolation is responsible for maintaining the genetic purity of westslope cutthroat trout in the North Fork of Fan Creek.

Unfortunately, continued isolation of this population cannot be assured due to the introgression of species in the East Fork. Therefore, it was recommended that the genetically pure North Fork population be protected from introgression by the placement of a semi-permanent artificial barrier on the lower North Fork. Although such a barrier will prevent westslope cutthroat trout residing in the mainstem from returning to the North Fork to spawn, relatively few fish make such a migration. The greater danger is from a single hybrid entering the North Fork, and the installation of an artificial passage barrier will prevent such an occurrence. Chemical reclamation of the East Fork and part of the mainstem of Fan Creek also was recommended to increase the amount of habitat occupied by genetically pure westslope cutthroat trout. This will improve the long-term viability and abundance of the population. Stepwise downstream reclamation, in conjunction with temporary barriers, will allow practicable-sized stream segments to be exterminated entirely. These segments then will be restocked with fish from the North Fork. After complete reclamation, the barrier on the North Fork will be removed and a permanent barrier will be installed in the mainstem, thereby restoring pure westslope cutthroat trout throughout the upper Fan Creek drainage. Our goal is to use the Fan Creek Restoration Project as a demonstration of a native fish restoration project involving chemical removal and movement inhibition of an exotic competitor.

Project Goals:
1. Assess the current fishery characteristics of Fan Creek to provide a pre-treatment baseline condition against which the success of the management program can be judged.
2. Guide project management incorporating state-of-the-art stream reclamation techniques.

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Researchers at the Montana Cooperative Fishery Research Unit conduct a telemetry...
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Introduced trout species have contributed to the decline of westslope cutthroat ...
Click here for an enlarged photo
As part of the effort to restore westslope cutthroat trout to the headwater trib...


Abundance, distribution, and genetic composition of westslope cutthroat trout and hybrid trout throughout the Fan Creek system will be assessed during summer 2004 before and after reclamation work is conducted. Recently collected data and samples of relevance have not been fully analyzed; we will complete the analyses in addition to conducting a comprehensive survey of existing salmonid populations in the system. Surveys will be repeated after reclamation efforts to assess the effectiveness of the project. The primary sampling tool will be multiple-pass electrofishing of isolated stream reaches to estimate absolute fish abundances therein. All captured fish will be weighed, measured, and tissue-sampled for genetic analyses. Comparisons of abundance, size, and genetic integrity of fishes before and after the reclamation will determine the effectiveness of restoration activities. Efficacy of barriers installed to prevent upstream migration of exotics will evaluated through tagging experiments. Project activities will be fully documented to assist in the planning of subsequent restoration efforts.


An evaluation of the techniques used to eradicate and exclude non-native fish was to be carried out in Fan Creek, Yellowstone National Park. However, recent findings have made the planned restoration there unfeasible. Cutthroat trout in the North Fork of Fan Creek were previously thought to be genetically pure (i.e., containing no genetic material from rainbow trout) and the National Park Service had planned to protect this “pure” population by removing the rainbow trout from Fan Creek and excluding rainbow trout from elsewhere in the drainage from immigration to it. Our plan was to use the Fan Creek restoration as a model case-history to study non-native eradication and exclusion techniques. However, protection of the cutthroat trout population in Fan Creek became a low priority for the National Park Service because subsequent genetic testing showed that the cutthroat trout in Fan Creek did contain a small amount of rainbow trout genetic material and were therefore slightly introgressed and not "pure." The planned restoration of Fan Creek was therefore canceled. We are replacing Fan Creek with several restoration projects that are being carried out elsewhere and are available for research. These include Vermejo Creek, New Mexico; Labarge Creek, Wyoming; and Cherry Creek, Montana. See the 2004-2005 Eradication and Exclusion project.

Graduate Research Assistant
Peter J. Brown
Montana Cooperative Fishery Research Unit
Department of Ecology, Montana State University - Bozeman
Bozeman , Montana 59717
Principal Investigator
Alexander V. Zale
Montana Cooperative Fishery Research Unit
Department of Ecology, Montana State University-Bozeman
Bozeman, Montana 59717


Updated: June 23, 2006
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