The Burren Smokehouse will be celebrating their 32nd anniversary this year - but smoking fish is a much older tradition than that. It goes back thousands of years when excessive salting of fish (and meat) and smoking it was necessary to preserve it for the harsh winter months, or for long travels across the sea. Sometimes fish was smoked for three weeks!
With the advent of modern transportation - trains - in the middle of the 19th century, it was all of a sudden possible to transport perishables fairly fast without having to preserve it so heavily. The salt content dropped and the smoking times were reduced. Today only minimum salt contents and mild smoking techniques are being used throughout the world as to get the best taste possible. So smoking fish is more a matter of taste than a necessity these days.
Alternatives to smoking was to cut the fish into thin strips and let them dry in the sun. Also it can be marinated to preserve it: salt it, add herbs and spices and bury it in the sand for a while (gravad lax). This is a Scandinavian technique, and the name "gravad lax" literally means "salmon buried in the ground".