Pasco steelhdr - I would argue that the idea of having hatchery strays in the system being a positive influence on genetic diversity isn't quite right because the genetics that are being spread around are "weaker". For example, if a hatchery takes eggs and sperm from 20 adults and turns it into 100,000 smolt (numbers are just for illustration of the point) there is genetic material from only 20 fish being artificially expanded into several thousand returning fish. This is further compounded by using hatchery fish as an egg source the following cycle, this magnifies an even smaller set of genes. In the wild the rate of return would certainly be lower for the same amount of eggs, but the genetics of the returning fish would be relatively much more diverse. Now as far as the idea of a river A fish being a "dumbed down" river C fish, this dumbing down is a nature of how small of a subset of river C fish were taken to establish the hatchery stock. For these fish to become "wild" by many definitions, only one generation must be spawned naturally, however, this doesn't make the fish comparable to the "native" wild fish. Many generations of natural production and lots of mixing of genes would be necessary to make them comparable to the native fish. However, this process of introducing new, what I would call weaker genes, if in big enough numbers, irreversibly affect the wild populations.
Matt Korb