End-of-summer means more fish kills statewide


The end of the summer is when fish are most vulnerable to changes in their environment, so even a small amount of pollution can cause major fish kills in Iowa’s waterways. (flickr/AgriLife Today)

The state Department of Natural Resources warns Iowans to consider how fish are affected when using chemicals and fertilizers.

The end of the summer is when fish are most vulnerable — temperatures are high, and dying and decaying plant life reduce dissolved oxygen in the water. Fish and other aquatic wildlife are stressed, meaning pollution can lead to more fish kills.

In 2016, the DNR reported 15 fish kills, 11 of which occurred in the latter part of the summer, after July 15. In the last two weeks, the DNR has investigated four fish kills around the state.

The DNR reminds farmers and homeowners that what they put on their fields or lawns will wash into waterways, where it could harm wildlife. Even a small amount of a chemical can cause serious damage.

“We have received several reports of small summer fish kills at many lakes, ponds, and a few streams throughout Iowa,” said Chris Larson, fisheries supervisor for the DNR in southwest Iowa, in a press release. “We have also had some fish kills caused by pollutants.”

Rarely, however, will all of the fish in a single body of water die at once. Usually the ecosystem can bounce back from a fish kill and balance its population again within a few years.

Farmers and homeowners can prevent pollution-caused fish kills by not applying chemical fertilizer or manure before it rains, and following disposal instructions on pesticide labels.

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