Setting the stage for conservation success: large- scale watershed renovation and re-introduction of cutthroat trout in the Rocky Mountain region of the USA

Summary

Two of the largest cutthroat trout restoration projects in the United States targeted native subspecies whose ranges had collapsed due to competition and hybridization with introduced trout. The Cherry Creek project on Montana's Madison River, a partnership between private landowner Turner Enterprises and state and federal agencies, chemically renovated about 100 km of stream and 3 hectares of lake habitat in four phases using the piscicides antimycin and rotenone between 2003 and 2010 to remove non-native rainbow, brook, and stocked Yellowstone cutthroat trout, isolating phases with temporary barriers behind a natural 8-meter waterfall. Roughly 37,000 eyed eggs and 8,500 young-of-year westslope cutthroat trout from wild and hatchery broodstock were introduced from 2006 to 2012; by 2012, post-treatment monitoring confirmed natural reproduction across the reconnected watershed with no remaining non-natives, expanding occupied habitat from 7 km to over 100 km. The companion Costilla Creek project in New Mexico and Colorado, the most ambitious cutthroat renovation ever attempted, aimed to restore roughly 190 km of stream and 20 lakes for Rio Grande cutthroat trout; an initial 2002-2004 treatment succeeded until a 2004 restocking event accidentally reintroduced rainbow trout, producing hybrids by 2007 that required a second rotenone treatment in 2008, after which the population recovered by 2010 with no hybrids detected. Both projects faced significant regulatory delay and public resistance to piscicide use. The project rates the Cherry Creek westslope cutthroat trout restoration Successful.