Federal and Illinois officials said Thursday that they will intensify efforts to find Asian carp in Illinois waterways this year but cut back on DNA sampling that has scored positive hits without resulting in the discovery of the invasive fish.
The $6.5 million plan released by the Asian Carp Regional Coordinating Committee "will focus on actions that have achieved tangible results," including removing Asian carp from the Upper Illinois River and other waterways below a set of electric barriers meant to keep them from reaching Lake Michigan, Illinois Department of Natural Resources Director Marc Miller said in a written statement.
"We believe removal efforts are working to reduce Asian carp populations in Illinois," Miller said.
The plan calls for intensive sampling of fish in waterways that connect the lake with the Mississippi River watershed to determine if any carp have breached those barriers, and two DNA sampling trips. But the discovery of environmental DNA will not automatically trigger a rapid response, as it has in the past.
Five response actions last year included 1,600 hours of surveillance over 27 miles of waterways with nets and "electrofishing," but no Asian carp were seen or captured above the electric barriers. Officials say they will forgo an automatic response until scientists can determine the significance of DNA discovery.
A federal study released in February found that Asian carp don't necessarily have to be present for their DNA to turn up in the environment. It is found in excrement, slime and scales from live fish, but also could be carried by storm sewers, fisheries sampling gear, fish-eating birds, dead fish carcasses, barges and sediments.
Scientists with the U.S. Army Corps of Engineers, the U.S. Fish and Wildlife Service and the U.S. Geological Survey are conducting a three-year study to try to answer questions raised by the repeated discovery of carp DNA in the Chicago area, hoping to refine how it's used for detecting the fish.
Officials say they also will test acoustic water guns that could scare away carp from crucial locations, and other control technologies this year.
Bighead and silver carp escaped into the Mississippi River from sewage treatment ponds and fish farms in the Deep South decades ago and have been migrating northward ever since.
Scientists fear that if the voracious eaters, which can reach 100 pounds, become established in the Great Lakes, they would out-compete native fish for food and threaten the lakes' $7 billion fishing industry.
Some state and local officials in the Great Lakes region want structures placed in the Chicago waterways to seal off Lake Michigan from the Mississippi watershed, although industry and local officials say that would hurt barge shipping in the Chicago area.
The U.S. Army Corps of Engineers says that at the end of the year it will present options to Congress to prevent invasive species from traveling between the two watersheds.