There does appear to be a correlation between number of smolts planted and resultant fishery. That's really obvious, plant more get more back.

But, it does seem, coastwide, that you need to put out a couple hundred thousand to have hopes for a reasonable fishery.

May be a number of reasons for this. Overwhelm smelt predators is one. Second is genetic. Plant, say 10,000 smolts (as WDG/WDW/WDF used to do, and you may have the progeny of three females. Poor genetics, few genetic resources maybe.

Look at the successful salmon programs. Who runs one with a plant of 10-20-30K?

This may mean that hatchery steelhead programs will need to be confined to areas where half a million can be planted after collecting the eggs from returning adults there. Take a good-sized facility to accomplish that. And bird netting so the smolts don't "vanish".

Have asked this question of program size to various Pacific Coast Steelhead managers but have gotten no response.