Lab tests indicate massive Iowa fish kill caused by dairy runoff

DYERSVILLE – The Iowa DNR received laboratory results last week confirming that ammonia toxicity in runoff from a dairy was responsible for an October fish kill in Dubuque County.

The DNR fisheries report shows 60,278 fish were killed along nearly seven miles of stream, including an unnamed tributary of Hickory Creek, Hickory Creek and Hewitt Creek. More than 42,000 were minnows, shiners, dace and chubs, according to a DNR news release. The remainder included primarily suckers, darters and stonerollers.

The DNR will seek fish restitution of $21,712.44, which includes a fish replacement value of $19,416.15 and the cost of the fisheries investigation.

Test results from water samples DNR collected Oct. 9 showed elevated levels of ammonia below a manure storage basin at the John Hoefler Dairy, New Vienna. Additional test results ruled out other livestock facilities and a field where manure had recently been applied.

The investigation started Oct. 9 at Highway 136 bridge in Dyersville, following a report of dead fish in Hewitt Creek. DNR staff followed dead fish upstream until they found evidence of manure washed into a stream.

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