The Basics of Smoking Fish

I've been researching the process of both hot and cold smoking for many years and during that time I've learned a lot, much of it from information freely available over the internet. In contrast however I've also read a lot of rubbish that has led me astray and in these instances I've had to find out for myself.
I've prepared this short article to give you an insight into what I've learned of the years so that you don't have to worry about what is good and what is bad advice. To make for easy reading I'll separate the two basic food that you will smoke when starting out and I'll start with fish and in particular salmon.
Normally I hang fish to smoke but that's not always the case with fish and in particular farmed fish. Many purists will tell you that farmed fish (especially salmon) isn't up to the job and you should always smoke wild salmon. The issue is with the texture of farmed salmon in that the salmon hasn't got the muscle development that you get with a wild salmon that's fought hard against the currents of the sea and rivers so for that reason it's necessary to smoke farmed salmon flat rather than hanging.
Farmed salmon is perfectly acceptable for smoking, it's just this issue with texture. I make no point about the merits or ethics of farming salmon.
Some believe that you can smoke stale fish and that the smoking process will somehow “bring it back to life”. Quite simply, don't go down this route. For a start it's not actually factual and secondly on a matter of principle, the better quality product you start with, the better the end product is too.
Many within the fishing industry will argue that frozen fish is as good as fresh because the freezing process takes place almost immediately after the catch and this is absolutely correct. Provided it's guaranteed that the fish is frozen when caught then this is a good source of fish for smoking and of course with every rule there's an exception............salmon.
When salmon is frozen, the moisture between the muscle fibers also freezes and when thawed this moisture washes out some of the natural oils in the flesh. If you ever have the opportunity to compare fresh salmon with frozen you'll notice that the fresh is just that bit firmer and that makes it easier to work with.
Moving on from oil I must write a little on the subject of fat content. First of all the fat content of a fish will inhibit the absorption of salt during the brining or curing stage and this then means that there's an element of guesswork involved when it comes to timing so all in all something that comes to you with experience.
The fat content of salmon will vary dependent on where it was caught. For example a fish that's upstream and has been “sitting around” will be thinner and have a lesser fat content than on that has been thrashing around in the lower area of the river. Going back to the merits of farmed salmon then it follows that the farmed salmon will lower in fat content and therefore require less brining than a wild salmon.