I agree with The King. You "cure" your fish with your brine/salt/sugar etc. The smoking process is used to impart flavor and to dry out the fish a bit, not cook it.

I usually run 2 or 3 pans of chips thru the my Big Chief right at the start and then let it continue on for an additional 6-10 hours, sampling along the way until I get the right consistency. I never let the temp get over 90-110 degrees; More than that and you are just cooking the fish.

A couple of tips that have worked well for me are:
1. I cut out a piece of grocery sac to the size of each filet piece and place it under each chunk as it is placed on the smoking rack. When done smoking the skin has adhered to the paper and it peels right off. It also keeps your smoker racks cleaner.

2. For the first 2-3 hours of the smoking process, I baste the salmon with pure maple syrup several times. It adds some sweetness to counter balance the saltiness of the cure, and adds a beautiful glaze.

Hope this helps.