M any species of salmon and trout are anadromous . In other words, they are born in freshwater, later live in the sea, then return to freshwater rivers or lakes to spawn . When a rainbow trout swims out to sea, it turns silvery. It is then called a steelhead.
Rainbow trout are very popular among fishermen.
But steelheads are considered trophies by many fishermen. The steelhead was adopted as Washington's state fish in 1969. I've never learned any details about its adoption. State Tree State Insect .