The catch of the grass carp was made April 7 near Prescott, Wis., where the Lower St. Croix flows into the Mississippi, said Jay Rendall, invasive species coordinator with the Minnesota Department of Natural Resources.

The grass carp is one of four species of Asian carp that escaped into the lower Mississippi basin after being imported into the United States in the 1960s and 1970s.

The others are the bighead carp, black carp and silver carp. The silver carp is known for its ability to leap from the water when startled.

Rendall said a small number of grass carp have been caught in the Mississippi River between Minnesota and Wisconsin over the past two decades, and a bighead carp was caught in Wisconsin's Lake Pepin in 2004.

The latest catch underscores the continuing threat from those fish, he said.

The Asian carp were imported to control nuisance plants in farm ponds. In the wild, they consume large amounts of the plants that sustain native populations of fish and wildlife.

http://www.startribune.com/531/story/391047.html 

So what do you think?  How long until they make it to the Upper Mississippi?  They are slowly making it further and further upstream all the time.  But that's how these things work.