She then covers the eggs and repeats the process. Adult salmon guard the site until their death. In late winter, eggs hatch from the redds. Young alevin in the gravel live off the nutritious yolk sac that hangs off their undersides for up to four months. Then they swim up from the gravel to start feeding on live prey.
Some species head straight to the ocean as fry, while others remain in the stream for another year.
Next, the smolt stage occurs. Once in the ocean, Pacific salmon migrate to the North Pacific Ocean, travelling in schools. After one to seven years, depending on the type of salmon, they return to their home rivers to spawn in the same stream they were born in. Physical changes vary between the species of salmon and are dependent on the amount of time between a salmon's entry into fresh water and spawning. The sleek and silvery body maintains its shape, but the female swells in the abdominal area and her snout slightly elongates.