Couple things, Salmo, as the rust leaves my memory.

Somewhere, in the early 80s, the idea was floating around WDF that PS Chinook were Springs and Summers. The Falls were actually imports from the Kalama around the turn of the last century. This made some sense to me (at least then) because Falls show up at low flow times and would have a harder time getting upstream. The idea floated around and died, but not did make sense.

I wonder if the increase in fisheries, and love of MSY, cratered escapement of all species so in stream productivity declined and that may favor the fingerling migrants.

Again, back in the 80s, WDF was running a recovery program for Dungeness Springs. Fish were raised to yearling because all of our successful Spring programs (Columbia) were yearlings. Nick, the tribal bio in the area, noted that all the Spring scales showed fingerling migrants; WDF stuck with yearlings because it works in the Columbia.

Maybe Columbia Chinook are different from PS Chinook. Nah, then we'd have to think.