Hot, dry weather and low water levels in Illinois is expected to trigger fish kills this summer in ponds, lakes, and rivers of the state. In June, the Illinois Department of Natural Resources (IDNR) began responding to reports of summer fish kills from private pond owners. The agency is anticipating more calls in the coming weeks.
Summer fish kills are reported almost every year and most are caused by low oxygen levels in the water. As temperatures rise and less rain falls, the water levels and oxygen levels drop in ponds, lakes, rivers and streams resulting in increased stresses on fish. Algal blooms are also typical and further deplete oxygen levels in bodies of water.
According to IDNR, roughly 99 percent of summer fish kills are due to the natural conditions that have reduced the oxygen levels below what fish can tolerate. Summer fish kills rarely result in total mortality of the fish in a pond, but can affect predator-prey balances.
Local IDNR fisheries biologists can be contacted by pond owners for recommendations if they experience a summer fish kill.
source: Illinois Department of Natural Resources