Below McNary dam its a boat fishing scenario, with Dick nite spoons, smallest size, red and silver is best, on a leader behind a diver of some sort. You have to get them to the bottom, 10-20 feet of water
Or you can use little flashy jigs behind the diver. The diver may be a plug with the hoods removed.
Hooked into a salmon once, chased it for 45 minutes before breaking it off on the 8 lb leader and light rod.
Note that columbia shad runs crashed the last two years. don't know why
I usually try to maximize my by-catch when shad fishing (assuming by-catch is open, that is). I've had the most success on small pink or chartreuse flies, my favorite is the Sharp Steelie. It wiggles in the current and sinks well without added weight.
Back East we used to go Shad fishing in the Delaware and the Hudson river. Shad were known as "poor man's salmon". All we used were very small gold hook shad darts on light line. Largest shad I ever caught was a 12 pound buck. Love shad roe cooked up in bacon fat. The rest of the fish we either smoked on oak planks or pickled. For whatever its worth. Jackd
Photo of some typical "Back East" shad darts.