The 1962 Rotenone Treatment of the Green River, Wyoming and Utah, Revisited: Lessons Learned

The 1962 rotenone treatment of the Green River in southwestern Wyoming and northeastern Utah was planned to depress populations of undesirable fish species, primarily common carp ( Cyprinus carpio ), before closure of Flaming Gorge Dam (1962), and upstream Fontenelle Dam (1964). Pre‐treatment surveys catalogued fish and aquatic insect communities, distributions of native and introduced fishes, and aquatic habitat. Near‐term, post‐treatment evaluations documented the effects of rotenone treatment on the aquatic fauna. Long‐term, post‐treatment assessments gauged development of sport fisheries for introduced rainbow trout ( Oncorhynchus mykiss ) and followed the status of native fishes and aquatic insect fauna. Fisheries biologists planned the project because the two dams would alter the river system to the disadvantage of native, big‐river fish such as razorback sucker ( Xyrauchen texanus ) and Colorado pikeminnow ( Ptychocheiius lucius ). Further, nuisance species, such as common carp introduced in the Green River system in the late nineteenth century, would benefit from the new lentic habitats. After‐project work showed that rotenone treatment depressed nuisance nonnative fishes and that none of the native big‐river fish populations were eliminated. Post‐treatment studies showed that native fish populations were far more impacted by impoundment than by the rotenone treatment. Careful pre‐treatment planning and well‐handled application of rotenone accomplished project objectives without eliminating native fishes.