Heavy Snow, Thick Ice Cause “Winter Kill” At South Dakota Lakes

LAKE OAKWOOD, S.D.- All of us are enjoying the warmer weather and the sunshine. You may, however, notice that there are some dead fish washing ashore on South Dakota lakes.

The winter season we went through is the culprit for that.

“With the winter we’ve had, it just hasn’t gone that way. Ice is still coming off the lakes, it is off completely on some, but not completely on others, and so we’re really just now seeing the volume of winter kill,” said Becky Graff, South Dakota Parks and Rec District Supervisor.

The volume of winter kill to this degree is all about the oxygen levels in the lake.

“The oxygen levels have dropped so low in the lakes that it actually starts killing off the fish,” said Graff.

High volume of snow on top of ice over the winter months cuts off a very important factor in plant life surviving and producing oxygen underwater.

“We can’t get sunlight through the ice, then that really depletes the oxygen levels in the lakes. Our culverts tend to, usually, stay open during wintertime which provides some open air, some refreshing there, but they did actually freeze over completely this winter,” stated Graff.

Those two factors combined to create an oxygen level of zero at certain test points throughout Lake Oakwood this winter, where the winter kill has been most severe.

Not all is lost, though, if you love to fish.

Graff said, smiling, “we didn’t have 100 percent winter kill, so there are still some perch, maybe even some northerns that are still in there. So, good luck to you, go ahead and try.

She says the lake will naturally re-supply itself over time, while South Dakota Parks and Recreation will re-supply lakes themselves, every two to three years.

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