Asian carp threat; so far...?

I keep reading how people in the midwest and the Chicago area in particular are apoplectic over the threat of the Asian carp making it into Lake Michigan, supposedly because it would decimate current Great Lakes fish stocks. Well, what has happened so far?? Have most of the other fish in the Mississippi and its tributaries been wiped out? None of the news stories about the Asian carp's

relentless spread up the Mississippi River system mentions this at all.