Like all other Pacific salmon, they are born in fresh water. However, sockeye require a lake nearby to rear in. Once hatched, juvenile sockeyes will stay in their natal habitat for up to three years, more than any other salmon. They then journey out to sea, where they grow rapidly, feeding mainly on zooplankton. They stay in the ocean for one to four years.
Sea-going sockeyes have silver flanks with black speckles and a bluish top, giving them their "blueback" name. However, as they return upriver to their spawning grounds, their bodies turn bright red and their heads take on a greenish color. Breeding-age males have a distinctive look, developing a humped back and hooked jaws filled with tiny, easily visible teeth. Males and females both die within a few weeks after spawning. Sockeyes are the third most abundant of the species of Pacific salmons and are a keystone in the North American commercial fisheries.