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Fish killed in bacterial bloom

The Yahara River in Madison was dotted with many pockets of dead fish like this after a major bloom of cyanobacteria formed on June 16 upstream in Lake Mendota. The bacteria can sicken or kill animals and humans. Fish likely died when decomposition of the vast bloom left water without oxygen. A similar kill happened on the Fourth of July on Indian Lake in western Dane County.

The Wisconsin Department of Natural Resources is investigating a large fish kill on Indian Lake in western Dane County, caused by low oxygen levels due to blue-green algae and a lake weed die-off.

Thousands of fish of all species — including northern pike, walleye, largemouth bass, bluegills, carp and bullheads — have died in the lake located in Indian Lake County Park, along Highway 19 west of Springfield Corners in the town of Berry.

The lake was being rehabilitated by county and Department of Natural Resources staff, by reintroducing game fish to a lake overtaken by less desirable fish.

“This was bad timing by nature,” said David Rowe, area fisheries supervisor for the DNR. “It will set us back.”

Rowe told the Wisconsin State Journal the fish kill was discovered on the Fourth of July.

“The fish are running out of air (oxygen),” he said. “There had been a blue-green algae bloom and then the curly-leaf pondweed starting dying back, which also uses oxygen.

“It’s a shallow lake, and it’s getting hotter, so it could get worse.”

Once the majority of fish die in Indian Lake, it’ll be restocked in the future.

Rowe said there wasn’t any plan to clean up the dead fish.

“We advise people to keep their pets from rolling in the dead fish and to avoid blue-green algae,” he said. “If you stick your toe into the water and you can’t see it, don’t go in.”

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Bill Novak is a general assignment reporter for the Wisconsin State Journal.