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Investigation shows what killed thousands of fish in two Iowa streams

DYERSVILLE, Iowa — The Iowa Department of Natural Resources has determined a cause to the source of a fish kill on Hickory and Hewitt Creeks in Dubuque County from earlier this week.

The fish kill was reported Monday, but the caller noticed the dead fish on Sunday following weekend rainfall.

Starting at the Highway 136 bridge in Dyersville, DNR staff followed dead fish upstream for about 5 miles to an unnamed tributary of Hickory Creek. The likely source of the fish kill is manure that washed into the stream from an animal feeding operation in the upper part of the watershed.

The investigation is ongoing as DNR awaits laboratory test results from water samples. DNR fisheries staff estimate thousands of fish were killed, including white suckers, stonerollers, minnows and creek chubs. An official count will be available later.

The Department of Natural Resources will “seek enforcement actions as appropriate.”