Hundreds of fish die from ‘spawning stress’ in Iowa lakes

A significant number of bluegill and crappie recently died at two southern Iowa lakes, the likely result of natural stresses the fish suffer during spawning season, according to the Iowa Department of Natural Resources.

The panfish kills were noted at Pony Creek Lake in Mills County and Little River Watershed Lake in Decatur County, said Chris Larson, a DNR fisheries supervisor.

“It’s pretty common this time of year to see a few dead fish,” he said, noting that fish might die at other lakes as well.

The fish kills are not expected to have a notable impact on bluegill and crappie populations of the lakes.

An angler reported the dead fish at Pony Creek, Larson said. He investigated the situation and estimated that he saw about 200 dead fish in different parts of the 80-acre lake.

They were all bluegill and crappie, he said, which indicates the kill was not the result of some sort of water contamination. If it were, Larson would expect to see bass and catfish carcasses as well.

“Overcrowding is one of the main causes of spawning stress in bluegills and crappies,” Larson said. “When too many fish are in a small area, they can become stressed and agitated. This can lead to fights and injuries that can cause stressed fish to become more susceptible to various bacterial or fungal infections.”

Water temperature changes, food availability and predators complicate spawning season, when the fish congregate and create and guard egg nests.

Those who see dead fish can report potential contaminations to the DNR’s spill line at (515) 725-8694. The department said quick reports are vital when fish of different species and sizes die in the same area or if there is obvious contamination from a pollutant.