"Koi are not very desirable for table fare, and they compete with species like rainbow trout that people tell us they want to catch," Hepworth said. "Smallmouth are a very direct threat to the native species within the Virgin River system. If they got out into the river system, not only would they compete, but more likely they would prey on and eat these native species that we're trying to keep from being endangered. "

In 2015, the population of smallmouth bass at Gunlock Reservoir got so out of control that the Division of Wildlife Resources treated the entire reservoir with rotenone. In the years following, Kolob Reservoir also received a similar treatment to deal with its runaway invasive species problem.