High heat and drenching rains kill Mississippi fish

Low oxygen conditions in and near the Mississippi River around La Crosse have killed hundreds of fish. Hot summer weather helped speed up plant decay in the water.

"You just get a lot of vegetation, duckweeds and stuff like that," said Minnesota DNR Lake City area fisheries supervisor Kevin Stauffer. "And eventually you'll start having some decay and start using up the available oxygen in small areas."

Oxygen levels near zero were measured in some backwater regions of the river in the La Crosse area.

Heavy rains then flushed that low-oxygen water into the Mississippi.

The dead fish included common species like blue gills and yellow perch as well as lesser numbers of largemouth bass and northern pike.

The fish were found both north and south of La Crosse.

The Minnesota DNR says the number of dead fish in such situations usually represents a fraction of the total fish population, because most are able to escape to areas with adequate oxygen levels.