Services:

Lone Willow Creek Westslope Cutthroat Trout Habitat Restoration

Issue:

Scientists from OASIS identified an isolated population of genetically pure native westslope cutthroat trout in a small tributary of the south fork of the Smith River in central Montana. Westslope cutthroat trout are imperiled in the Smith River watershed with only four known populations existing. A long established irrigation reservoir on the creek had prevented upstream migration of non-native trout thereby protecting the native cutthroat trout population. The ranch on which the creek flows is a working ranch and historically the reservoir is drawn down significantly each year during the irrigation season. In addition, cattle have had unrestricted access to the pond and stream corridor. The result has been annual degradation of water quality and quantity in the pond and the loss of quality in-stream habitat. Two potential migration barriers also existed in the form of undersized culverts at road crossings. A new landowner and the Montana Department of Fish, Wildlife & Parks (MTFWP) were interested in developing restoration plans for the creek and the pond, which was regarded as a potential deep water refuge for the stream's fish population during extreme conditions.

Solution:

To create more favorable conditions for long term survival of the westslope population, OASIS generated designs to alter irrigation operations, increase overall pond depth, restore and improve the structural integrity of the reservoir, fence off the stream corridor and replace passage barriers with oversized culverts using natural streambed simulation techniques. Design tasks included initial fisheries inventory, stream simulation culvert design, hydraulic design of pond outlet and spillway structures, reservoir grading plans, dewatering and fish transplant plans. OASIS also provided construction oversight and revegetation services.

Results:

The reservoir is now a secure fish migration barrier with a constructed spillway capable of withstanding a 100 year flood. Accumulated silt has been removed from the reservoir and irrigation operations have been altered so that a full pool is maintained throughout all seasons. The fish population in the stream will now have the reservoir available during the heat of summer and through extreme winter conditions, providing an increased level of population security in the system. The MTFWP will be collecting genetic material from the secured population and will then use remote station incubators to re-introduce westslope cutthroat trout into other stream systems throughout the watershed.

Case Studies

Montana Department of Fish, Wildlife & Parks

Scientists from OASIS identified an isolated population of genetically pure native westslope cutthroat trout...
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Montana Department of Transportation

OASIS created wetland mitigation sites (banks) for MDT to provide credits that offset the loss of wetlands caused by road construction...
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Private Landowners

The owners of the PMD Ranch and the Nelson Spring Creek Ranch had interest in restoring a small unnamed spring creek...
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Montana Department of Fish, Wildlife & Parks

The Chadbourne Irrigation Diversion Dam on the Shields River near Clyde Park, Montana was degrading...
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