Sockeye salmon (Oncorhynchus nerka) — also called red salmon or blueback salmon in the United States — is an anadromous species of salmon found in the Northern Pacific Ocean and rivers discharging into it.This species is a Pacific salmon that is primarily red in hue during spawning.They can grow up to 84 cm in length and weigh 2.3 to 7 kg. Juveniles remain in freshwater until they are ready to migrate to the ocean, over distances of up to 1,600 km. Their diet consists primarily of zooplankton.his species is a Pacific salmon that is primarily red in hue during spawning. They can grow up to 84 cm in length and weigh 2.3 to 7 kg. Juveniles remain in freshwater until they are ready to migrate to the ocean, over distances of up to 1,600 km. Their diet consists primarily of zooplankton.