Sockeye salmon is unique in that it can live in both fresh and salt water.
They first hatch from their eggs in freshwater streams and lakes and then migrate to the ocean. At this point, they are bluish in color with silver tinges.
When they are old enough to breed, they swim back to the same freshwater nursery where they were born to father their own offspring.
When this happens, they change color. Their bodies turn red while their heads turn green. After they spawn, they die and the new generation repeats the cycle.