The twin lakes of Hennepin and Hopper are full of water and life again, after the Wetlands Initiative and the Illinois Department of Natural Resources (IDNR) completed a six-month effort to remove the invasive common carp.
“We were surprised to see the water level return to normal so quickly,” said Gary Sullivan, the Initiative’s senior restoration ecologist at the Dixon Waterfowl Refuge in Hennepin, Illinois.
The Wetlands Initiative drew down the lake level last fall and winter to rid the lakes of the carp. Groundwater and spring precipitation have rapidly filled the lakes since the end of the drawdown.
“Now the return of the native flora and fauna has been unbelievable. Plants are coming back like they were shot out of a cannon, and it’s even early in the growing season,” Sullivan said. “We have seen sago pondweed and water celery, two of the most important species for fish and waterfowl that were once extremely abundant but are now rarely in the Illinois River Valley.
“Even the cattails, which had been nearly completely obliterated in recent years by a population explosion of common carp, are back in full force.”
The cattails provide important habitat for the yellow-headed blackbird, a threatened species in Illinois that has now returned to the Dixon Refuge. The bird has again been observed in the refuge this spring, after being absent last year due to the degraded habitat.
Black terns, common moorhens, pied-billed grebes, and American pelicans have also returned to the refuge.
Water clarity in the lakes has also improved due to the rehabilitation. "We can see down to 9 feet deep in the water now," Sullivan said. "When the carp were present, you couldn't see your fingernail when your hand was in the water."
In April, IDNR restocked the lakes with more hundreds of thousands northern pike, muskie, and channel catfish fry, said Wayne Herndon, IDNR fishery biologist. IDNR has also stocked the lakes with breeding stock of large-mouth bass, red-spotted sunfish, brown bullhead, bowfin, spotted gar, star headed topminnows, and pumpkin seed. This month, they added 500 6-inch muskie.
The 2,600-acre Hennepin and Hopper Lakes Project, located along the Illinois River about 40 miles north of Peoria, is owned by the Initiative and several nonprofit organizations and is managed by the Initiative. Since 2001, the Initiative has been restoring the historic lakes to create a high-quality backwater lake habitat in order to improve water quality, provide wildlife habitat, and to offer a place for the public to enjoy Illinois’ historic native landscapes. Prior to 2001, the lakes had been drained for 90 years to support corn and soybean farming.
