MISSOURI VALLEY – The Iowa Department of Natural Resources (DNR) will treat Nobles Lake with a low concentration of rotenone to eliminate rough fish. Nobles Lake, 95-acre cutoff oxbow lake located in Harrison and Pottawatomie counties on the Missouri River floodplain, was inundated and infested with numerous invasive and river fish species during the floods of 2011 and 2019.

The dryer than normal conditions and historic low flows in the Missouri River has nearly drained Nobles Lake, providing ideal conditions to remove rough fish. Invasive species like silver carp, bighead carp, shortnose gar and common carp have a negative impact on water quality and wildlife habitat by suppressing aquatic plants. “The most effective method to eliminate the remaining fish population is to apply rotenone under the ice this winter,” said Bryan Hayes, fisheries management biologist with the Iowa DNR.

Rotenone is used world-wide and has been since the 1930s.  It is a common tool that fisheries managers use for fish removal. Rotenone is a naturally occurring compound that comes from the roots of a tropical plant in the bean family. The Iowa DNR commonly uses the commercially available formulation, five percent Prenfish, which has been approved for fisheries management by the U.S. Environmental Protection Agency (EPA).

Nobles Lake is part of a larger 236-acre Iowa DNR Wildlife Management Area primarily used by waterfowl hunters and bird watchers.