The Combination of Mechanical and Chemical Removal Techniques to Restore and Enhance Native Cutthroat Trout in a Small Drainage in Northwestern Utah

Native fish restoration is often complicated by such factors as drainage size, habitat complexity, and identifying a source of fish for post-treatment stocking, among others.  A small drainage in northwestern Utah identified for restoration contained an abundant population of brook trout that dominated the lower reaches but had not yet overtaken the native Yellowstone cutthroat trout (YCT) in the headwaters.  We determined that a combination of chemical (rotenone) and mechanical (electrofishing) methods to remove brook trout could be successful if undertaken properly.  With no good source of YCT for post-treatment repatriation, and because the headwaters contained more native trout than nonnative, we opted to protect the headwater YCT by constructing a temporary barrier mid-drainage.  Subsequent to barrier construction, we completed mechanical removal upstream of the barrier and chemical treatments below.  Three full electrofishing passes through the upper drainage were completed each year in 2011, 2012, and 2013, as well as two passes in 2014.  After hundreds of brook trout were removed in the first eight passes, brook trout were not present in passes 9-11.  Rotenone treatments were completed below the barrier in 2013 and 2014.  The temporary barrier will be removed during 2015, pending evaluation of treatment success via electrofishing.