Run timing probably evolved from the time that the rivers began to be reasonable for the fish to enter to spawn. The depth and temperature had to be appropriate.

WDFW and their hatchery program perverted all that. They always select the earliest returning fish for their hatchery program, so they have achieved earlier run timing for the hatchery fish, usually weeks before the wild run. Back in the 70's hatchery fish and wild fish came into the rivers together.

And Puget Sound has far more hatcheries than the Olympic Pennisula which still has many intact wild runs.
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Give a man a fish, and you'll feed him for a day; give him a religion, and he'll starve to death while praying for a fish.