SOLON – The Iowa Department of Natural Resources (DNR) received a report of dead fish in Terry Trueblood Lake in Iowa City, and Mohawk Park Lake and Cedar Lake in Cedar Rapids, on Feb. 27.
DNR fisheries staff found about 1,000 dead bluegill, 1,500 channel catfish, 225 carp, 100 largemouth bass, 400 trout, 150 wipers (hybrid striped bass) and several thousand gizzard shad on March 1 at Terry Trueblood Lake. Almost all of the dead fish at Cedar Lake and Mohawk Park Lake were gizzard shad.
Winter kills happen when a combination of ice and snow blocks sunlight from reaching aquatic plants, which in turn, stop producing oxygen. The longer the snow and ice cover lasts, the less oxygen is in the water.
Winter fish kills are common on Iowa shallow lakes during long winters with lots of snow cover. “Terry Trueblood Lake, Cedar Lake and Mohawk Park Lake are very shallow to start with and dry fall conditions have caused lower lake levels,” said Paul Sleeper, DNR fisheries management biologist. “Our larger eastern Iowa lakes are not experiencing winter fish kills.”
Signs of winter kills are visible shortly after ice out when fish that died during the winter float and are blown to shore. In certain lakes, like Rathbun, Black Hawk, Storm and Coralville, these dead fish are often a source of food for channel catfish that will go on a feeding spree. Many anglers see this as an early season fishing opportunity for trophy-sized channel catfish.
Fisheries staff are watching lakes and ponds with low oxygen levels that are at risk of having a winter fish kill. Many Iowa lakes and ponds are still under ice, so additional smaller, shallow ponds and lakes might have winter kills after the ice disappears.