Hennepin and Hopper Lakes in Illinois have been closed to all public sport fishing while The Wetlands Initiative (TWI) and the Illinois Department of Natural Resources (DNR) renew their effort to remove invasive common carp from the lakes. The two agencies announced their initiative in a joint statement today.

DNR fisheries biologists identified a large number of common carp in the lakes located 40 miles north of Peoria along the Illinois River in a survey conducted last year. TWI ecologists and others observed that vegetation in the lake was decreasing.

“Once the carp reach a tipping point, they begin to take over,” said Paul Botts, TWI’s executive director. “We could see the vegetation vanishing before our eyes.”

TWI is a non-profit organization that manages the Sue and Wes Dixon Waterfowl Refuge at Hennepin & Hopper Lakes. TWI has been restoring the 2,700-acre site from row crops to diverse native ecosystems since 2001. In 2009, TWI partially drained the lake and applied fish toxicant rotenone to remove the common carp until a healthy marsh habitat returned. Carp among other native and sport fish were restocked and native flora and fauna returned. But by the summer of 2011, ecologists could see the vegetation was decreasing.

The next removal efforts will directly address what remains of the drain tile system which carp were using for shelter from the toxicants during the 2009/2010 removal effort.

“We aren’t going to repeat the same draw down steps,” Botts said. “Rather, we are going to do something more sophisticated: we are dividing the remnant drainage ditches into segments to create smaller wetland cells that can be drained independently. This will allow us to drain each cell completely and make it easier to locate and disable every last drain tile line.”

Photo: Tim Creque

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