State biologists expect a spring fish kill on the Big Eau Pleine reservoir in central Wisconsin will be even bigger than 2009 when tens of thousands of fish were wiped out of the waterway.
Wisconsin Department of Natural Resources experts suspect the fish kill has already started, judging from reports by area ice anglers.
The DNR said oxygen levels in the Eau Pleine are so low fish can't breathe. Nutrient-rich sediment and organic material decays and sucks the oxygen out of the water. The ice limits the air and light from replenishing it.
The Marshfield News-Herald reported that after the fish kill four years ago, state and local officials repaired and improved an aerator to boost oxygen levels in the reservoir.