Fry plants were the first thing tried with hatcheries. No real evidence that it worked very well.

I think that one of the biggest problems in hatcheries is when fish are incubated and/or reared in water other than their natural water. Apparently, many cold-blooded organisms have enzymes (which are inherited) that function best at different temperatures. A fish that evolved to incubate in really cold water will not do well incubating in warmer water, and vice-versa.

Fry plants would still be limited by rearing capacity of the stream. Fry would probably work well with pink and chum, pretty well with sockeye and fingerling chinook, fairly poorly with coho and yearling chinook, and even worse with steelhead.

We don't need "quick fixes". We have to let the fish that emerge from the gravel have a chance to survive.