Tough question, as every smoker seems to be different and variables like ambient temperature, thickness if fillet and fat content all have a big effect. On a day like this I would use my Big chief without a cover and would begin checking about four hours into the process. After a couple of hours rotate the top and bottom racks for a more uniform batch.

The best hint I can give you is to break a piece in half to check for doneness. If it’s close to as done as you like pull it immediately. The fish will continue to dry as it cools. If it’s almost as done as you like when you pull it out, it will be just right when it’s cool