McGREGOR - A combination of high flood waters following heavy rains and warm summer temperatures are contributing to fish kills in some areas of the Big Sandy Lake system near McGregor.
The tributaries of Big Sandy Lake were nearly devoid of dissolved oxygen which is currently resulting in fish kills - most notably in the Sandy and Prairie Rivers and the bays closely associated with the inlets of these rivers.
Water runoff from flooded peatlands, hayfields, and other normally dry areas carries partially decayed organic material to streams and rivers. When those organic materials reach warm water, the resulting microbial activity consumes the dissolved oxygen fish need to survive. Fish can become stressed from warm water temperatures alone, but the combination of warm water and less available oxygen is resulting in higher than normal fish mortality in the system.
Other areas of the Big Sandy Lake are holding more normal levels of oxygen and so far are experiencing no fish loss.
"While the Big Sandy system has seen floods of this magnitude in the past, they have always been in spring when water is much colder, so we are on un-travelled ground this year," said Rick Bruesewitz, Aitkin DNR area fisheries supervisor. "Water temperatures and duration of the flooding will determine the extent of the fish kill but we know fish populations are resilient and usually rebound without much intervention."