Harsh winter leads to increased fish kill in small bodies of water

Although winters with heavy snowfall and subzero temperatures might be good for snowmobiling and ice fishing, it can be deadly for life beneath the ice.

Reports of fish kills are up in McHenry County after one of the coldest and snowiest winters the area has seen in years, according to the Illinois Department of Natural Resources.

When ice and snow cover the water, light cannot penetrate, which slows the growth of algae and plants that produce oxygen for fish. The dissolved oxygen levels are too low for many fish to survive.

Shallow bodies of water, such as Lily Lake in Lakemoor, have been especially affected as deeper ponds or lakes have a greater volume of oxygen and can better sustain fish.

Lily Lake has seen between 200 to 300 dead fish wash ashore this month, according to Lakemoor Village Administrator David Alarcon.

“It’s been the worst winter cold-wise and snow-wise,” Alarcon said of his five-year tenure at the village. “In the past, we’ve had significant snowfall, but it wasn’t this frequent. This year there was basically one snowstorm every weekend.”

Alarcon called the fish kill a “moderate loss,” and he said the village is considering restocking the lake in the future.

“The mayor has been considering possibly doing a restocking program, but it would need approval with the IDNR,” he said. “It hasn’t been restocked in many years.”

Restocking bodies of water is one answer to fish kill, but a more permanent solution would be to install a compressor that blows air throughout the pond, said Andy Plauck, IDNR district fisheries biologist for McHenry, Kane and DuPage counties.

“This winter really drives home the need for aeration for smaller bodies of water,” Plauck said. “You can restock [the fish population] and hope it resets itself, or you can curb the problem by installing aeration.”

The compressor sits on the shore with a hose that pumps bubbles throughout the water. They cost anywhere from $1,000 to $15,000 depending on the size of the body of water, Plauck said.

In addition to Lily Lake, Spring Grove Hatchery Park, Rush Creek Pond in the McHenry County Conservation District, and many neighborhood ponds experienced higher than normal fish kill, Plauck said.

Plauck said this year the IDNR has seen species of fish die that are normally not affected by the low dissolved oxygen levels. Common carp, channel catfish, bullheads, and young-of-the-year sunfish have all been spotted washed up on area shores, he said. In years past those species have made it through the winter.

“Just about every year we get phone calls about fish kills,” he said. “It’s natural. The weaker fish die off. But this year we did see species that are typically tolerant of low dissolved oxygen levels die.

“A lot of ponds had ice cover starting before Thanksgiving and lasting until the beginning of April.”

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