There are five species of Pacific salmon: Chinook, Chum, Sockeye, Pink, and Coho. Salmon begin their life as eggs in gravel beds, hatching into alevin then fry before developing silver scales as smolt. As adults, they migrate to spawn and die. Dams block migration and change habitats, killing many salmon through turbines or predation. The Elwha Dam was removed to aid salmon migration, though sediment release polluted water temporarily. Preserving salmon supports both ecosystems and industries like fishing.