Expert? LOL
I simply grew up in nearby Philomath, so just had the advantage of being in the Alsea's back yard. My dad was also raised in the area; as were several other family peeps "back in the day". I even had a great-great uncle, that homesteaded in Lobster Valley (a few miles south of the town of Alsea).
The Blueback (sea-run cutts) will run somewhat in unison w/ the 'nook and coho runs. When there is enough rain, the 'nook run peaks in late September/early October. The silvers and bluebacks are not far behind.
When peeps are bobber fishing tidewater for nooks (at this time); I'll sometimes troll for bluebacks, as they are not getting a lot of angling pressure. The usual flasher sets (Ford Fenders, Beer Cans, etc) work fine. Tag on about 24" of leader w/ a nightcrawler and Voila! Fish on!
You can also have lots of success right now above tidewater, while the water is low and clear. I prefer bobber n' worms or spinners. Or, a bobber and black woolly bugger w/ my spin rod. I have also caught some on single salmon eggs, drifting w/ little weight.
However, there is a highly effective fly pattern. I have not tried it, but I have heard nothing but good reports. It is called the Borden Special. It was developed by Bob Borden of Monmouth. Bob now lives in Monroe, and his shop is only about 30 minutes south of Corvallis. Here is his website:
And here is a Caddis Fly Shop video on how to the Borden Special:
Borden’s Special: Sea Run Cutthroat Fly Pattern
I would not expect many of the bluebacks, to go too much further upstream that the hatcheries. They are a stocked fish. But, on occasion, one might be found higher up.
Enjoy.
TD
P.S. I really think that we should ban together and get the spellchecker software peeps to "recognize" the word "blueback"...LOL.