I’ve seen multiple studies showing that the Asian Carp diminish the numbers of sport fish present, sometimes fairly dramatically. Again, the food chain is being eaten away from under them. Plus, even very young bass and such eat plankton, so, they are affected too.
Put more simply, a given body of water will only support so much biomass in the form of fish. If the water is full of Asian Carp, other species will be diminished, especially if many of the carp are too big for the predators to handle.
As for the dam / electric fence proposal, no, that’s not for the Tennessee or Cumberland Rivers. The carp are now well past (upstream) of KY Lake and Lake Barkley, so, the only practical solutions there will have to be in the way of commercial fishing, or biological warfare.
However, you may be reading my proposal for the Illinois River as being “bigger” than it is. To restate, and modify slightly, having had more time to think it over:
My proposal is really just an expansion of what’s already been done.
http://ens-newswire.com/2013/01/12/chicago-fish-fence-fails-to-deter-giant-asian-carp/
(The title is a misnomer — so far, the fences are helping. But they are not sufficient in themselves, and Rotenone then is applied.)
It turns out there are already two “electric fences” on the Illinois River System. (At least one is actually in the shipping canal connecting the Illinois River to the Chicago River, via the Des Plaines River and the Shipping Canal, leading to Lake Michigan.) In conjunction with the Lockport Lock and Dam, and applications of Rotenone, so far, these measures have stymied the advance of the Asian Carp toward Lake Michigan. A few carp may have made it past the fence, but, so far at least, they do not appear to be a breeding population. (If there are two male AC in Lake Michigan, and 2 female AC in Lake Michigan, the chances of any of them finding a mate to spawn with are VERY low.)
So, assuming the existing “electric fence” in the canal is a convenient starting point, place more “electric fences” downstream (ie., toward the Mississippi River), followed by a modest dam — the dam to be as far downstream from the existing “electric fences” as possible. (Note that the confluence with the Kankakee River likely limits how far south / downstream the new dam can go. But, Joliet is upstream, which may help deter birds carrying Carp eggs or Carp upstream.) Under normal circumstances, the river pretty much just flows through the new dam. It is only closed for a fish kill operation, therefor locks are not needed. The biggest problem I see is having enough water storage capacity to “back up” the river at a time of low flow, for a couple days.
Basically, the idea is to impede migration of the fish, and, if need be, have a ready made “kill zone” on hand.
(Note that since water flows from Lake Michigan into the Chicago River to the canal to the Des Plains River to the Illinois River, and IIRC the inflow can be interrupted, the concern about water storage capacity for a fish kill operation may be invalid.)
That consideration is among factors making me want to fish for those Asian carp using a roundhaul net that circles and then closes immediately, keeping most everything in the net alive ----one reason being so that game-fish species could be sorted from Asian carp, and returned to the waters the game-fish came from -- if removed from the water, at all.
My apologies for back-tracking to fisheries considerations, but there's a bit more along those lines...
Gillnets are species selective only in mesh size, and in just where and when they are set --including what parts of the water column the entangling meshes of gill, and/or trammel nets are placed in. Once a fish is caught in a gillnet, it doesn't necessarily die right away, but after some time does usually die, with this varying depending upon the type of fish, and just how gilled, or 'wedged' into the mesh, and how long the fish is in the net, etc. The fish that get away, or else those thus caught but chosen to be put back in the water -- can still suffer some amount of injury, which can lead to death, or lesser dysfunction later on. Sorry again to go on about commercial fishing aspects, when you were talking about eradication through blockage and chemical-like treatments...
As for the electric fence contemplations; I think I see better what you were intending regarding an overall plan, but the "fences" that are there presently being used did cost a pretty penny, which is something to consider The power consuptions of those things are rather high, and there's always risk that things could go haywire (leading to serious injury and death of human beings) given enough time such systems were in place.
The additional note you provided there at the end would bear more investigation;
How to make "a dam" that is usually "open"? I'm having trouble envisioning such a creature unless there be some side-sluice (or multiples of those) which could be closed off. One question, touched upon diagonally in your added "(note...)" -- what kinds of river flow does the Illinois require? That does vary, and quite a bit, too, depending upon weather conditions and need for sufficient drainage at any one time.
I must admit I don't know enough about the physics of the river systems to comment any further than idle speculation...