Even for ice anglers, this long, cold and snowy winter has become too much of a good thing.
The thick ice that has enabled them to walk safely for months on ponds and lakes has now become a death sentence for many of the fish they pursue.
“I would be nervous if I were a farm pond owner. With another three to four weeks to go, it’s going to be a pretty bad winter for fish kills,” said Department of Natural Resources fisheries biologist Paul Sleeper.
Deep snow over thick ice has cut off the penetration of sunlight, which drives photosynthesis in aquatic plants, replenishing the oxygen consumed by fish, said DNR fisheries biologist Chad Dolan.
When oxygen levels get too low, the fish die, he said.
Dolan, whose office is at Lake Darling State Park in Washington County, said he has not received any reports of fish kills yet but expects to when the ice melts and losses become apparent.
“It is one of the worst winter fish kills in more than 20 years for us down here in Keokuk County,” said Tom Monroe of Sigourney, an ice fishing enthusiast who helps several farmers manage their ponds.
It’s worse in southern Iowa, Monroe said, because pond water levels already were low from the drought of 2012.
“A mild winter helped the fish survive last year, but they are really suffering now with low water and all the snow-covered ice limiting the amount of oxygen available to fish,” he said.
Monroe said ponds that provided excellent fishing a few weeks ago now show no signs of life. Electronic sonar units used to indicate the presence of fish have gone blank, he said.
Linn County farmer Curt Zingula said he noticed dead fish floating Sunday in a small patch of open water on one of his two ponds.
Zingula said he since has enlarged that opening in an attempt to get more oxygen into the three-acre pond, and he plans to deploy a de-icing compound to further expand the hole.
Raccoons have been coming down to the hole to take advantage of the free lunch, he said.
Zingula said last year’s late summer drought lowered his ponds to 3 feet below normal pool.
“They have not had any fresh water coming in since last July,” he said.
Monroe said ponds with aerators have been faring well, but both Dolan and Sleeper noted it is too late to try to install an aerator now.
Monroe said ponds over-stocked with grass carp in an effort to control excess vegetation have been among the first to succumb to fish kills.
Iowa has more than 85,000 ponds, most of them in southern third of the state, according to Iowa State University fisheries extension.
Dolan said both the DNR and private stocking companies are available to help pond owners replace lost fish.