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Fish Barrier Protects Native Trout

by Joseph Platz, Miles City FO
photos courtesy of Bairco Construction

Yellowstone cutthroat trout

The Crooked Creek fish barrier project will protect a genetically pure population of Yellowstone cutthroat trout.

men constructing the barrier

Construction in progress on the Crooked Creek fish barrier.

completed fish barrier

The Crooked Creek fish barrier will keep nonnative trout from migrating upstream into the native Yellowstone cutthroat trout habitat.

A recently completed fish barrier on Crooked Creek in the Pryor Mountains will benefit genetically pure populations of Yellowstone cutthroat trout (YTC).
Crooked Creek begins in the Custer National Forest, flows through BLM and private lands, and then enters Bighorn Lake in Wyoming. The Crooked Creek barrier project protects and expands one of three genetically pure populations of YCT on BLM-administered lands and one of six pure YCT populations on lands administered by the Custer National Forest.
Native to Crooked Creek, the isolated headwater population of YCT (a sensitive species in Montana) was once protected from nonnative salmonid invasion by a naturally formed boulder barrier; however, extensive debris flows after a high intensity wildfire in July 2002 altered this barrier, making it passable by upstream migrating nonnative salmonids. Brook, brown, and rainbow trout survived the debris torrents and occupy the lower drainage, but the remaining YCT population is at a high risk of localized extinction. 
To prevent competitive interaction and hybridization with nonnative salmonid species, the YCT population had to be physically isolated. The fish barrier project was designed to accomplish that goal.
A temporary barrier was constructed in August 2006 as a short-term solution, but managers knew it would not be an effective obstruction during high flows. The barrier stayed intact, but did not prevent brown trout from entering YCT habitat. One year after construction, about 120 brown trout were found upstream of the temporary barrier.
The Custer National Forest funded a permanent barrier design contract with Great West Engineering of Helena, which was completed in the spring of 2007. The Billings Field Office completed an environmental analysis at about the same time. Several issues affected the project in terms of the design and environmental analysis. First, the project is located in a Wilderness Study Area, which limits disturbance and affects visual resources and construction activities. Second, the project is located in almost inaccessible terrain, typified by steep rimrock canyon walls. Third, cultural resources are located adjacent to the project area. As a result, the design was very complex and the cost elevated.
A contract was awarded to Bairco Construction from Lovell, Wyo., in early August 2007. Later that month, Bairco began work on the project, completing it in early October. Construction was challenging. It involved erecting a cable tram to haul materials and equipment into the project site, clearing the work site, and diverting the stream. Additionally, the concrete was mixed on site, with heavy manual labor. Challenging, but worthwhile. The end product is excellent.