When salmon mature, most species embark on a journey to return to the place where they spawned. They travel upriver from the ocean, often fighting strong currents and predators such as bears. This journey can sometimes be as long as hundreds of miles.
As they become ready to mate, salmon undergo a physical change. They often become darker in color with reddish areas, and they may develop a large hump and sharper, larger teeth. Their jaws often extend and become even more hooked (this curving jaw projection is known as a “kype”).
Once they reach their destination, the salmon will spawn –females will lay their eggs which males will fertilize. Many salmon do not survive the journey, and even those who do will die soon after spawning, as the trip takes an enormous amount of effort and energy. Salmon also undergo a period of rapid deterioration due to an explosive release of hormones that prepares them to make this long and dangerous excursion to mate.