Smoking is one of the oldest methods of preserving fish or any other meats for that matter. Long before there were refrigerators and freezers our fishing ancestors learned to use a combination of salt and smoke to keep fish from spoiling. Today, smoking is no longer "necessary," but it remains popular for the flavour it gives to such fish as salmon, trout, mackerel, eel, and kippers.
Smoking methods vary but all are based on a few common principles. First, the fish is treated with salt, either in the form of strong brine or a surface coating of dry salt. During this curing stage (which can last for anywhere from a few minutes to many hours depending on the size and density of the fish) a two-way exchange takes place with much of the moisture drawn out of the fish and some salt soaking in. This combination of reduced moisture and salt inhibits the growth of spoilage bacteria, a basic principle of all cured meats.
Many types of fish can be hot-smoked. Don't expect to slice hot-smoked fish the same way you can cold smoked it will just crumble if cut too thin. Cut hot-smoked fish into cubes, chunks, or thick slices, or just flake it apart along the natural seams between the muscles. In this form, the fish is ready to use in salads and other cold dishes or gently warmed in a pasta sauce.