From what my father-in-law was thinking, he surmised this. Yes, chums head right out into the salt as soon as the hatch. Pinks do somewhat the same, but maybe not quite so fast. Sockeye can hang out in lakes for a year or so, while coho and chinook lead pretty similar lives, compare to the lives of the other three. They hang out in the river for a while, then decide to go to salt.

I may be horribly wrong, so feel free to dorrect me.