Dead fish removed from Glen Ellyn pond

Hundreds of dead fish have appeared and disappeared twice this week at a pond in the Maryknoll Estates subdivision in Glen Ellyn, but officials say there’s an easy explanation.

“It seems as though it’s probably caused by a winter kill,” said Maureen Brehmer, an environmental protection engineer with the Illinois Environmental Protection Agency, who visited the pond late Thursday morning. “It’s probably caused by low oxygen in the pond. It’s very simple.”

When ice sits on a body of water for a while before melting, Brehmer said, the oxygen level of the water drops. Some species of fish — including the gizzard shads that made up the majority of casualties at the pond — often are killed by the drop in oxygen level, said crews from Marine Biochemists, a lake and pond management company with an office in Elburn.

Monique Wilhelm, a member of the Maryknoll Estates Owners Association who directs pond maintenance, said she called Marine Biochemists to clean up the second round of dead fish Thursday morning.

But by the time the crew arrived, many of the fish found dead Wednesday already were gone. They may have been eaten by other animals, sunk to the bottom of the pond, or flowed into the DuPage River, she said.

The same happened with the first round of dead fish, which Wilhelm said neighbors spotted on the shore Saturday, before they vanished without a cleanup effort.

And while the carcasses may have given off an unpleasant odor Saturday and Wednesday, several neighbors who stopped by the pond Thursday said they no longer smelled anything.

Those arriving after 11 a.m. saw nothing but an oval-shaped pond with ducks swimming through small ripples caused by wind and geese grazing along the edge. The pond is bordered by several townhouses on the north, about 10 houses on the west, prairie on the south, and a string of power lines and then Interstate 355 on the east.

Wilhelm said after hearing from the Marine Biochemists crew, she is confident the water is not toxic.

“Part of the problem was that the gizzard shads overpopulated,” Wilhelm said.

Officials from the DuPage County Forest Preserve said winter kills are fairly common, and conditions were ripe for the phenomenon this year because of the large amount of snowfall.

Betty Kohler, president of one of the two associations representing Maryknoll townhouse residents, said she received a few calls Thursday morning from residents who saw a Wednesday evening TV report that showed large numbers of dead fish floating along the pond’s surface. But with the fish cleanup already completed, she said the issue seems to be under control.

The two townhouse associations and the homeowners association plan to split the cost of the fish cleanup because they share maintenance responsibility for the private pond.

Marine Biochemists normally performs tests on the pond’s water and algae during the summer, and will continue to do so, Wilhelm said.

“We discussed the possibility of doing a study in the summer to determine which fish are still left,” Wilharm said.