Glowball,
The Riffe coho that are 12" or longer are last year's coho smolts, not this years'. They are no longer trying to migrate downstream. They seem to have accepted Riffe as their "ocean" much the same as Great Lakes salmon do. This is the wrong time of year for them to be on a spawning migration. The fact that they are cruising around the "inlet" to Riffe appears to be a feeding migration, not a spawning one. Similar behavior occurs with some land-locked Atlantic salmon in large lake systems with large inlet and outlet rivers, as part of a feeding migration pattern. I don't know what they are feeding on, maybe it's the sub-yearling chinook that are still dizzy from their swim through the Cowlitz Falls turbines. That might explain the success of Dick Nites and other small sliver spoons.
What I have yet to learn is if these land-locked coho actually become sexually mature in the fall and if they are capable of successful spawning. It's had to dedicate time to research that, as it would be the same time I'm downriver trying to catch real sea-run cutts and silvers. Let's see, fly rod or jig rod? See what CFM has done to me? Life just keeps getting more complicated.
Sincerely,
Salmo g.