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After ice-out, some Minnesota lakes seeing fish kill

ST. PAUL—It's fish kill season in Minnesota (and yes, that is different than fishing).

All around the state, hundreds of dead fish are washing up to the shorelines of small lakes, including about 10 lakes in the east metro. But officials aren't concerned.

Winter kill is standard, especially in longer winters like this year's.

"It's a natural process," said Jim Levitt, a fishery specialist for the Minnesota Department of Natural Resources. "It can actually benefit the lake in that the fish that are left have less competition. There's more food for them, they might have a growth spurt, and there will be bigger fish for the next year or two."

Lakes have a certain amount of oxygen in them when they freeze in the fall or early winter. The fish use that oxygen all winter and into the spring. In bigger lakes, there's enough oxygen for most of the fish to survive, but in some of the smaller lakes, the fish slowly start to die as the oxygen depletes.

Quick lake warm-ups can also cause bacterial infections, which kill the fish as well.

"Spring can be stressful on fish," Levitt said. "They've gone all winter maybe not feeding as much, it's been cold, and now the water all of the sudden warms up and it's spawning season so they're spending a lot of energy on that."

As a result, most of the fish kill calls come within a month of ice-out.

Sometimes, thousands of fish will die from winter kill, but even those high numbers are not cause for alarm, Levitt said. Although the DNR doesn't have exact numbers of fish in each lake, several thousand fish might still be less than 10 percent, he said.

The DNR typically only investigates if fish in large lakes are dying or if unusual species of fish are dying.

Raccoons, turtles, pelicans, eagles and other animals eat the dead fish, eliminating a need to clean them up.

What to do

Call 800-422-0798 to report any fish-kill sightings. The DNR will determine whether an investigation is necessary.

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