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DNR to eliminate the remaining fish population at Hickory Grove Lake

  • 7/21/2020 12:48:00 PM
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COLO - Story County Conservation (SCC) and the Iowa Department of Natural Resources (DNR) are partnering to renovate the remaining fishery in Hickory Grove Lake. The DNR will treat Hickory Grove Lake on August 4th (pending workable weather conditions) with rotenone, a botanical pesticide, to eliminate the remaining fish population.

An attempt was made last fall/winter to drain and dry the lake basin to rid the lake of common carp, grass carp, and black bullhead. These injurious fish species reduce water clarity, destroy aquatic plants, and prevent the fishery from reaching its full potential. 

Unfortunately, common carp were observed this spring as the lake was refilling. “The most effective method to eliminate the remaining fish population is to apply rotenone to the lake basin and tributaries,” said Ben Dodd, DNR fisheries management biologist.

Eliminating injurious fish species is an imperative and final step to achieve water quality and fishery improvements. 

The project area includes Hickory Grove Lake and a portion of the associated watershed. The treatment area includes both public and private property. A map of the specific treatment area is available at Treated public areas will be posted with placards and closed to public use until the placards are removed. Private property owners adjacent to treated water have been notified. It will likely take 48 hours for the rotenone to dissipate from flowing streams and 7 to 14 days from ponds and the main lake. Avoid human and pet contact with water in the treatment area, do not use dead fish for food or feed, and do not use treated water to irrigate crops or lawns.

Rotenone is used world-wide and has been since the 1930s. It is a common tool that fisheries managers use for managing sport fish, improving water quality, and managing endangered species. Rotenone is a naturally occurring compound that comes from the roots of a tropical plant in the bean family. The DNR commonly uses the commercially available formulation, 5 percent Prenfish, which has been approved for fisheries management by the U.S. Environmental Protection Agency (EPA).

The EPA has concluded that the use of rotenone for fish control does not present a risk of unreasonable adverse effects to humans or the environment. The EPA certifies all pesticides based on use according to label directions, which the DNR is equipped to fulfill these obligations. 

Find more information about rotenone and the treatment area at