Under Statewide General Rules, subsection "Harvest Rules":

"You may not possess or use live fish for game fish bait"

This, of course, only applies to game fish and WDFW does not list salmon as game fish.
Under Statewide Definitions, Game Fish are defined as:

"bass, burbot (freshwater ling), catfish, crappie, grayling, northern pikeminnow, peamouth chub, yellow perch, northern pike, tiger musky, sucker, sunfish, trout (including steelhead and kokanee), landlocked chinook, coho and Atlantic salmon, walleye and whitefish"

Northern pikeminnow? Peamouth chub? Sucker? Sheesh!
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PS