You'll find bows and cutts throughout the system. In addition, though, I believe that it is also Catch and Release only. But, double check the regs...I may be mistaken.
But, I'd suggest trying for blue backs (sea run cutts) in Tidewater or just above. If you have a boat, I would troll tidewater for them with a Ford Fender and worm or spinner/spoon.
Or, if you can grab some flies before you head out...nab some Borden Specials (Two Rivers Fly shop in Albany, or Back Country Fly shop in Corvallis has them). They were designed specifically for Alsea River blue backs.
There should be some Nooks in Tidewater now too. Bobber and Bait is the way to go...or trolling with bait/spinners.