Smolt is one of the juvenile stages of the salmon and steelhead (which it reaches at about 2 to 3 years old). It's the portion of the lifecycle where it leaves fresh water for the first time and goes to the sea where it will then live out most of its adult life. However, this part of the journey is deadly and many won't make it to adulthood.The origins of the word smolt is unclear but believed to come from Old English meaning "Serene, Bright". During the transition from "Fry" to "Smolt" the fish scales will turn silver.