I smoked some cod a month or so ago (just before I joined SMF), at the request of my boss - who was used to buying it at local delis. He mentioned he didn't see it very often any more. I told him, if I could find the right fish, I would certainly smoke a batch for him.
I did some research on the "right" kind of cod, and found that "true cod" or sablefish was what I was looking for, but black cod would work too. All of my readings indicated that one should use only fresh cod, if hot smoking was the cooking method - frozen would yield a drier finished product, due to the moisture loss during freezing. Whole Foods had cod only sporatically, but Santa Monica Seafood had it regularly - and it was on 'sale' the week I bought it. $14.99/lb *gasp*
The filets were fairly thin, only a scant 3/4" at the thickest point, so I needed to be careful about how long I was going to brine the fish. I brined overnight, about 8 hours. I can't track down the brine recipe I used, but I know I opted to cut back on the salt (I used fine sea salt), bringing it in line with the sugar (white). I added peppercorns, lemon zest, fresh ginger and a few bay leaves to the other ingredients. Pulled from brine, dried with paper towels and set on racks in front of a fan for several hours.
All of my reading indicated it may take up to 6 hours for the filets to come up to temperature. My total cook/smoke time was 4.5 hours. I started at 100 for an hour, bumped to 120 for 2 hours, 160 for the remainder of the time. I did this before I had a
AMNPS to supplement the smoke at the low temps, so I didn't get any smoke until after the first hour. Used a probe thermometer to keep tabs on the IT. I used applewood chips.
I did notice a couple of "hitchhikers" tried to escape during the cooking, but didn't make it through the higher temps. Thankfully, I am not squeamish and I just removed them.
I let the pieces cool and then vacuum-packed them for distribution.
I did try a piece. It was tasty, but a little 'fishy' for my liking, and thankfully not too dry - even the very thin tapered ends. Lightly smoked. I prefer smoked salmon. My boss was very pleased and very appreciative. He did mention he remembered the stuff from the delis was always yellow-colored - not from the smoke, but more from a coloring - saffron, maybe tumeric?
Side note: Although it was smoked outside, it was brought inside to cool, and it made the house smell fishy. Odd.
Good luck!