LAKE VIEW, Iowa | All fish in Black Hawk lake were killed Thursday, part of the largest Iowa lake renovation in more than 25 years.
Crews worked with the Iowa Department of Natural Resources in criss-crossing the lake, applying the fish toxicant rotenone to kill all fish remaining in the 922-acre lake. The chemical, according to the DNR, affects only organisms with gills because rotenone is taken up through gills and interrupts oxygen transport.
Birds, mammals and other organisms were not harmed, the agency said.
Black Hawk Lake was closed to boat traffic Thursday and fishing is closed. Fishery crews will pick up dead fish as they surface next week.
The lake won't be restocked until spring, as waters will need the winter to detoxify.
"This is not the end of the Black Hawk Lake renovation," said Ben Wallace, fisheries biologist for the Iowa DNR. "We are just getting started."
The Black Hawk Lake Protective Association will install a barrier at the lake outlet to prevent carp from re-entering the lake during times of high water. Carp and other invasive species that stir sediment at the lake bottom have reduced the population of other fish species while contributing to the lake's poor water quality.
"It's the bad fish that are hurting our lake," said Steve Snyder, owner of The Bait Shop at Lake View. "If we eradicate these carp we can get vegetation to grow, which helps support other fish who lay eggs. It gives them the habitat they need."
Snyder and Jim Garrels, owner of Blackhawk Marine, admit business will take a hit this year and next as the new fish population grows.
"Along with the fish kill, we'll lose some of our fishers the next three to four years," Garrels said.
"Everyone will have to take their medicine. We all must put up with a little pain to get there," Snyder added. "If we continued as is, it's just a so-so place. They think we have the chance to become an excellent fisheries here."
Wallace expects to see a marked improvement in the water quality and clarity, and aquatic plants returning to the lake, once the carp are gone. "This spring, Black Hawk Lake will essentially be a new lake and when these fish are released, they will grow pretty quickly, with some reaching acceptable size in two to four years, depending on the species," he said.
Low lake levels allowed the fish kill to be conducted Thursday in a rare period when lake volume has been reduced by up to 45 percent, due to the 2012 drought. Fewer chemicals were needed, and lower water levels eliminated habitat around the edge of the lake where carp may have taken refuge.
Instead of fishing this popular tourist destination in 2013, anglers may head to nearby Storm Lake or the Black Hawk Pits near Lake View, a water resource renovated early this year by the DNR and stocked with thousands of adult channel catfish, largemouth bass, walleye and pan fish, all collected from Black Hawk Lake ahead of Thursday's kill.
A commercial fishing operation, Wallace said, removed 130,000 pounds of rough fish from Black Hawk Lake before Thursday. Those fish were sent to various markets, including Omaha and New York.
Black Hawk Lake draws an estimated 250,000 visitors per year to Lake View, a Sac County city named Iowa's Tourism Community of the year in 2011.