Horn signals or a radio call may not get a response when on big open water like you PNW folks have, but you aren't out anything by giving it a shot when in a potential situation. We feel the same way when dealing with other recreational boaters. But at home, where the ship channels and ICW define the waterways, I always make a quick call on the VHF if in doubt. Well, except for the shrimpboats... heck, about half the time as they come in, there's no one at the helm. :shock:
See and avoid.
Even running the cruiseboats on Jackson Lake this summer, I used horn signals as we left the dock. This wasn't standard procedure there, and one of the other captains asked me, "What's the point?"
"Well, all those kayaks, canoes, and small boats may not have a clue why I'm honking three times... but, they DO turn their heads and look. Better that they know we're out here and moving than not."
Shortly after that, all the captains used horn signals.
One of our own here learned something about up/down river expectations and what constitutes a "fishing vessel." Education is a good thing.

Better to know and use that information than to just assume no one else does and not.
Best wishes,
Jim B.