There are 66 species of salmon, trout, whitefish, and their relatives . Species in this family are found throughout the northern hemisphere and are some of the most important commercial and sport fishes in the world. Because they are so popular with fishermen they have been widely introduced to other parts of the world. Some species are endangered or have become extinct as a result of overfishing and the destruction of spawning streams. Fish in this family are almost all “anadromous,” which means that eggs are laid, hatch, and develop in freshwater streams, young fish then travel downstream to the ocean where they spend as much as several years at sea feeding and growing. When they are ready to breed they swim upstream again to spawning sites in freshwater streams. Some species die immediately after they breed. Salmon, trout, whitefish, and their relatives generally need cold, clean waters to survive and breed. They are large, predatory fish, growing up to 1.5 meters and mainly eating other fish.