The environment that the Carps enjoy is fast moving water, like Spring high water, for spawning and then they like to move to the slow water of a River and/or backwater lakes and channels to feed.
Since the accidental release of the four species in the South in the 1970's, they have been inexorably moving upriver. The first real impact on the public's knowledge of them was, when the reports started coming out of the Illinois River. I remember that it was about 15 years ago when I heard of a female jet skier on Peoria Lake who was hit by a Silver Carp resulting in being knocked unconscious and inflicting a broken jaw. The popularity of this video brought the issue to a whole new audience.https://www.youtube.com/watch?v=hN2gMP3Q2Z4
These are the Silver Carp, which are disturbed by boat noise and leap out of the water. Some researchers say that boat noises may mimic their predators in Asia, the fresh water dolphins and their survival instincts cause them to jump at noise.
The Lower Illinois River is heavily infested with both Bighead and Silver and the big concern is that they will enter the Great Lakes at Chicago and threaten a $7 billion dollar fishing economy. The upriver movement has been stalled about 80 miles south of Lake Michigan. The sustaining population hasn't moved upriver in 26 years.
The Wabash River in Indiana is heavily infested. The Carps have begun to establish a presence on the Ohio River and are moving up the Ohio's other tributaries, the Cumberland and Tennessee Rivers.
The Missouri is also heavily infested and the Carps have moved up the James River as far north as Jamestown, ND, where they are stopped by the Jamestown Dam. For those that have thought that the Carps won't survive in colder waters, know that Jamestown is on the same latitude as Fargo.
As far as the Rivers we care about, the Upper Mississippi is heavily infested, though not as bad as the Illinois, as far north as Lock and Dam 19 at Keokuk, IA. The 42 ft high dam has slowed them down with the only way they can move upriver is through the Lock. Reports of a reproducing population in the Quad cities area seem plausible. What we have been seeing, when reported by commercial anglers, seem to be those aforementioned Scouts. The St. Croix, from what I have been able to ascertain from netting and eyewitness reports seems to have a reproducing population, there are too many sightings to think that we are just seeing Scouts. It would be very difficult to properly ascertain the level infestation of the St. Croix because it's extreme depth would mean bringing in deep water netting gear to accurately gauge the extent of their numbers. The biggest fear in the State of Minnesota for potential infestation is the Minnesota River. The biology of the Minnesota, a slow moving River with many backwater lakes and nutrient rich waters that are prevalent in the agriculture dominant Valley. The same environment that the Minnesota River has is very similar to the Illinois River's.
Next: What is being done and what will our future look like.