Paul, it depends on what kind of fishing you want to do. August is a great month for salmon and here is one of the least expensive fishing trips you can take. Just south of the Creek Street Bridge there is a hardware store that rents fishing rods and sells one day fishing licenses. You can rent a rod for a couple of hours and fish right from the bridge and catch your limit. Since you can't take the fish with you, catch and release is the appropriate method of fishing. You will catch a mix of salmon with some large ones thrown in for good measure. You don't have to go much further to get quality fishing.
If you want to do a fly-in trip then I would contact Seawind Aviation in Ketchikan. They will arrange to fly you into one of the hot lakes in the Misty Fjords region with a fishing guide. I haven't done it, but itt is on my radar for my next Alaskan trip. Hope this helps.