Salmon fishing or ocean fishing? You are there at the very best time for salmon so I would consider this as an option. In Ketchikan, try fly-in fishing in the Misty Fjords with Seawind Aviation. I would book it on my own, but wait until I got into the port simply because the weather in September can be quite dicey. If you book it in advance, the operator may want to fish if the water is quite rough or it is raining cats and dogs, and you might not want to.
Hope that helps.