Hi JW....I've smoked lots of whole salmon filets but never salmon steaks so my advice may not be good advice. This week I did two whole filets from Costco, (skinless filets because I hate the fishy-oily taste that the skin imparts on the finished product). Just prior to putting them in the smoker I cut them crosswise into three large sections. I cut them on the seafood rack so they appeared just like a whole filet. I intended to give them to some friends that like my salmon so that was the reason for cutting them. I don't know whether you are using steaks cut vertically through the backbone or boneless steaks cut from a filet. How thick are they and are they skinless or skin on?(yuck!)If they are 1" or more thick I would cut back on the wood because of the additional surface area exposed to smoke. On a filet I use 2 oz. hickory and 2 oz. of apple. The 140 D. internal temp. sounds OK I guess. I don't use a themo probe on fish, I use my finger and eyes to test for doneness. I have tried several different recipes for smoked salmon including Cardogs but keep coming back to Andi's method (seafood archives) especially her "dry brine". Follow her method to the letter and you won't be disappointed. Typically I use a temp. setting of 155D. for 4 hrs.
As to the question of farm raised versus "wild" salmon, two weeks ago I did a test. Costco had wild Copper River salmon filets as well as their normal farm raised salmon so I bought one of each. They appeared identical and the texture was the same except the wild salmon had less color. I prepared them both the same way, smoked them together at the same time and I couldn't tell the finished product apart...and I make my living cooking. Nor could my friends tell the difference. My guess is the smoke masks any subtle difference between wild and farmed. If you are concerned about chemicals, you should probably stop eating farm raised meat too
and I recently read that the mercury level in west coast ocean fish is reaching critical levels...so what are we supposed to do in this age of genetic engineering, not eat?
Hope this helps a little.
CB