Good question NM. Unfortunately, on the coast, the best we can do is form an opinion based on the collaborative observations of guides & anglers.
The Quillayute Tribe has been less than cooperative in helping to gauge the returns we're seeing off of this. I honestly can't say if it's through indifference or untruthful reporting on their part. A good example of this was an "unofficial comparison" of reported tribal catch versus a rough estimate of numbers of Snider fish caught by attendees of the Guides' Association meeting. The sport catch of those in the room was over four times that of what the tribe reported ... obviously, the numbers the tribe was giving didn't jive ... unless we've magically bred fish to swim around nets
The best we can do is to look at total escapement, which is up despite a lack of help from the tribe in respect to harvest ... as well as spawning activity within that section of river.
Russ Thomas, an older fella (in his 80's), has walked the streams of the area for over 60 years keeping an eye on things. He's noticed a large increase in spawning activity with the creek itself, as well as the mainstem 'Duc in that area, and even some nearby creeks that have not seen fish in some time.
I believe it helps to have the destination of the fish in non-angling waters as we do here so you don't have a terminal end area fishery.
And after some discussion with Sparkey last night on chat, there is one other thing that I think is important to note regarding the project in this area:
These streams are still catch and kill and a number of the fish that are used for this project are donated by clients that would otherwise have taken the fish home. Obviously, this isn;t the case in my boat ... but the majority of fish come from catch-and-kill boats and I'm happy to see these fish go towards helping out the river rather than simply filling up the bottom of a cooler.