Briney then chucks the Asian bighead carp onto a slimy heap of others writhing on the bottom of the boat.
For example, no bighead carp DNA was detected anywhere, including in Iowa where the fish are known to be.
Some of the Chicago DNA was found in Lake Calumet, where a live bighead carp was caught in 2010.
Of particular concern are silver and bighead carp, which gorge on plankton microscopic plants and animals that virtually all fish eat at some point.
He defended Illinois' efforts to block the advance of silver and bighead carp toward the lakes by hiring commercial fishermen and operating an electric barrier, but acknowledged more needs to be done.
Bighead and silver carp imported from Asia decades ago have infested the Mississippi River and many of its tributaries.
Bighead and silver carp gobble enormous volumes of plankton, a crucial link in the aquatic food chain, while silver carp sometimes collide with boaters by hurtling from the water when startled.
"These results support the conclusion that bighead and silver carp have not yet become established in Minnesota, " said Steve Hirsch, director of the Ecological and Waters Division for the Department of Natural Resources.
Croix rivers found little evidence of bighead and silver carp, according to a study released Thursday that concludes that while the invasive fish are present in Minnesota, their numbers are likely relatively low.
Laboratory analysis turned up 58 positive hits for bighead or silver carp in the Chicago Area Waterway System a network of rivers and canals linked directly to Lake Michigan and six in western Lake Erie.
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