I think most fish is cold smoked, no? Hot smokers, the kind people have in their backyards, are higher temperature (200* and up) and suitable for meats. For a cold smoker, you would have to have a place to place/hang the fish and a firebox located somewhere nearby, so that the smoke can be channeled to reach the meat, but not most of the heat from the fire. I saw Andreas Viestad smoke little trouts once by hanging the fish over a big stock pot with some wood shavings on the bottom, placed on a burner. The heat from the burner made the wood shavings smoke but not burn and it stayed pretty cool in the pot (with the lid askew). Neat idea, but maybe not so practical with big salmon! (Though, maybe you could rig up a rack of some sort, a colander at the top of the pot with a little rack of some sort inside, and put a couple of salmon fillets in it...? Thinking out loud, but definitely something worth experimenting with.)
ETA: Here is the Video mentioned above:
http://www.youtube.com/watch?v=_gxocblSJxw