The sockeye salmon is both salt- and freshwater fish. It is best known for its migratory behavior.
Sockeye salmon are born in freshwater rivers then travel to the ocean to grow and mature. When it is time for sockeye salmon to breed–three or four years later, they swim back to the very same river where they were born. There they breed and bear young before swimming back to the ocean. The term for this repetitive migratory behavior is anadromous.
The period when sockeye salmon’s breed is called the spawning season. Sockeye salmon spawning season happens every year between the months of June and September. During spawning season, millions of sockeye salmon make the difficult, often dangerous journey back to where they were born. Some travel up to 1,500 miles (2,500 km) to get there.
A sockeye salmon can pinpoint the exact place where it was born using its strong sense of smell. Each river has a distinct smell. A sockeye salmon monitors the smell as it swims upstream, stopping only when it recognizes the right spot. This spot becomes its spawning ground.
During much of the sockeye salmon’s swims upstream it encounters barriers such as rocks, rapids, and waterfalls. This does not stop the sockeye salmon; it can thrust itself up and out of the water to jump over barriers. Along the way, sockeye salmon are hunted by larger fish, birds, otters, and seals. Going upriver, sockeye salmon are even hunted by bears.
A mature sockeye salmon can measure up to 33 inches (84 cm) long and weigh up to 15 pounds (7 kg). Its lifespan is about three to five years. Sockeye salmon differ from other salmon in one remarkable way: before spawning sockeye salmon have steel-blue heads and backs and silvery sides, but during the spawning season after they leave the ocean and enter the river of their birth, their heads turn bottle-green and their bodies bright orange. Also during the spawning season, male sockeye salmon develop a hooked nose.
Sockeye salmon are found from the northern Bering Sea to Japan and from Alaska southward to California. The scientific name for the sockeye salmon is Oncorhynchus nerka.