There is a last little bit about steelhead and hatcheries that isn't often talked about, even by the researchers. I have tried to get them to consider it, but....

For years, the WDG steelhead model was to incubate and rear the eggs on the warmest water possible. This promotes faster growth so age-1 smolts are easier to achieve. Basically, they were cultured on groundwater. Salmon were basically cultured on surface water which more mimicked natural conditions.

As cold-blooded animals, their enzyme systems are not only genetically inherited but often selected for temperature ranges. A fish that lives in 50 degree water year around will not function well in 35 degree and it is genetic.

So, in order to develop "local" stocks we, for example, started to culture the Puyallup steelhead at Voight's rather than Chambers/South Tacoma. They performed poorly because they simply could not function well in the water temperature regime. I think that this is one reason why hatchery steelhead perform poorly when asked to function as eggs and juveniles in the wild. Not all the reason, but big part.