BTBW hit the nail on the head with that one. They produce "viable" fry but exceedingly few of those juveniles survive to perpetuate their lack of genetic fitness. That in itself is what has helped to considerably slow down the genetic pollution of wild stocks by hatchery fish... the crappy genes just don't have a good mechanism to perpetuate themselves.

The only problem with the hatchery:wild cross that Angg described is it wastes the reproductive potential of that wild hen for that spawning cycle. If that is the only spawning run she would survive, then basically she made no more contribution to future returns than if she had been bonked.

Should she survive to make a return trip upriver for a second spawn, she may get another chance to successfully perpetuate her genetic fitness... that is if the spawning gravel isn't overrun by a bunch of hatchery males.