But there is another reason why Ancient Irish hunters would set camps along rivers. Fish. And one fish in particular: salmon. We know that the Bronze Age Irish had been catching and eating salmon on large scales using massive fish traps and weirs. Indeed the oldest fish traps found in Europe were found in Ireland and were used for catching salmon 8000 years ago.
Fish first needs to be scaled, gutted and filleted. This can be done in the stream or river or lake.
After the meat and fish was cleaned, and before it is salted, it needs to be cut into thin strips to enable deep salt penetration and proper aeration and smoke exposure.
The strength of the brine is a matter of preference. Brining duration depends on the type of smoking you want to do. One method of determining the ratio of water to salt is to put all the fish or meat you want to salt into the trough and then cover it with water. Then just keep adding salt to the water until no more salt will dissolve in it. You can test the concentration of the brine by dropping an egg into the water and adding salt until the object floats.
The salting period is 3 weeks.
The thing is for either type of salting, the trough would have to be covered with a wigwam, to protect it from rain.
After the salting, birning is finished, the remaining salt in the brine can be reclaimed by boiling the brine in the trough using super heated stones. This is the exact same procedure used for extracting salt from brine that I described in my post about a possible use of fulachta fiadh as salt extraction facilities.
Now that the fish or meat is salted, it needs to be quickly rinsed in fresh water and it can then be hang and smoked.
The reason why smoking preservers food is predominantly because a number of wood (or peat) smoke compounds act as preservatives. Phenol and other phenolic compounds in wood smoke are both antioxidants, which slow rancidification of animal fats, and antimicrobials, which slow bacterial growth. Other antimicrobials in wood smoke include formaldehyde, acetic acid, and other organic acids, which give wood smoke a low pH—about 2.5.
In order to be smoked the fish or meat needs to be hanged off some kind of frame or placed on some kind of rack which is then placed over a smoldering fire.
A simple wooden rack like the one below is sufficient for short hot smoking.