The first step in the process of smoking is taking good care of your catch. When you land a fish, whack it on the head, bleed it, gut it and ice it immediately. You also want the fish to go through rigor mortis and relax again prior to filleting. This results in a flesh that absorbs salt and smoke more readily. I don't scale fish I plan to smoke.
Smoking works great with either fresh or previously frozen fish.
Store-bought electric smokers use an electric element as a heat source. You place wood chips in a pan that sits on the heat element. This is a hot smoking process. For my money, these smokers run too hot. My smoker has a sliding front door.