Columbus residents walking in Mill Race Park over the past couple of days encountered an unpleasant smell and a more unpleasant sight — dead fish floating on the surface of Round Lake.
This sight was the result of a natural phenomenon known as lake turnover, an annual occurrence. Director of park operations Casey Ritz said that the dead fish likely rose to the surface over this past weekend. Park employees removed the fish on Monday using nets.
“…We’ll continue to monitor it,” Ritz said. He said that the parks department usually disposes of the dead fish by composting them.
Ritz was unable to give an estimate for how many fish were found on the lake this summer. In 2018, about 500 fish were found on the lake surface. Many of these were catfish, carp and suckers, species that are found near the bottom of Indiana rivers and lakes, according to parks employees.
As previously reported by The Republic, Indiana Department of Natural Resources spokeswoman Lt. Angela Goldman said that lake turnover is common during the summer, and usually happens in shallow ponds and lakes, which warm up quickly as temperatures rise.
When a cooler rain follows the pond water warmup, the warm pond water stirs up particulate matter on the bottom of the pond that was not previously exposed to oxygen, decomposing rapidly and drawing oxygen out of the water, according to naturalists. If this happens fast enough, there isn’t enough oxygen in the water to support the fish and they die.
Parks workers said the fish get into Round Lake when there is flooding in the Flatrock River, which runs through the park.
Fish that happen to be in the lake as the water recedes stay there until the next flood, when they have a chance to leave the lake and return to the river.
