Generally speaking, you can smoke all kinds of fish but mackerel is a classic. I have tried trout as well, the end result is also good. Clean the mackerel, remove the heads and wash them very well. In the abdominal cavity, insert a 1-2 bay leaves, black pepper kernels and allspice and stuff with salt.
In a suitable container, put salt on the bottom, arrange the fish next to each other tightly and add more salt - to cover them. Leave in the fridge for 24 hours.
Wash the fish well (save the bay leaf), if necessary, you can leave it for half an hour to an hour in cold water to soak. Dry the fish very well and brush with oil or olive oil. Use toothpicks to hold the abdominal cavities well open. Leave the prepared fish to sit for an hour while you prepare the smoker.
There's a wide variety of smokers available in stores, but if you do not have one, let me offer you an easy alternative. Find an old pot. At the bottom, add around a finger’s width of oak, beech or fruit tree shavings. Put the set aside bay leaves on the bottom.
Drape the fish by hooking it with string to a stick or use a metal slab, for example. Prepare a suitable cover. Put the pot on the stove until the tree chips get warm. Close tightly, remove it from the heat and leave it for about an hour.
Check the fish – it should have a nice yellowish tinge. If there's not enough smoke, you can warm the pot up again, but in most cases an hour - hour and a half is enough.
If you're using a smoker, maintain a temperature of around 140°F (60 °C). The fish will be ready in about 4 hours.