DNR: Cause of summer fish kill in SE Minnesota stays a mystery

The deaths of thousands of fish in the south branch of the Whitewater River last summer likely came from a mix of conditions following heavy rains on July 28 and not from any single chemical, biological or environmental cause.

That's the conclusion of investigators from three state agencies who were unable to nail down the cause of the fish kill in the river. About 9,000 to 10,000 fish died, including brown and rainbow trout, dace, white suckers and sculpin, the Minnesota Department of Natural Resources said.

The DNR, the Minnesota Department of Agriculture and Minnesota Pollution Control Agency examined tissue from dead fish, analyzed water and soil samples .

It's often hard to determine the cause of fish kills in river systems, said DNR spokesperson Chris Niskanen.

"Many times the agent, whether it's sediment or chemical, that was involved in killing the fish can quickly move downstream and become diluted and not leave any real obvious clues as to what it was," he added. "It's unfortunate we can't figure out what killed the fish, but not unprecedented."

The fish populations, he said, should bounce back without additional stocking.

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