Sockeye salmon Pacific salmon, feed extensively on zooplankton during both freshwater and saltwater life stages. They also tend to feed on small aquatic organisms such as shrimp. Insects are part of their diets at the juvenile stage. Sockeye salmon exhibit many different life histories with the majority being anadromous where the juvenile salmon migrate from freshwater lakes and streams to the ocean before returning as adults to their natal freshwater to spawn. Similar to most Pacific salmon, sockeye salmon are semelparous, meaning they die after spawning once. Some sockeye, called kokanee, do not migrate to the ocean and live their entire lives
Kokanee salmon of landlocked sockeye has occurred more than once with different kokanee populations, showing genetic differences between populations. Most evidence points to events that land-locked the lake-type sockeye (which spawns in streams and lakes, rather than tributaries like the sea-type sockeye, but is still anadromous and spends most of its adult life out at sea), which evolved into the non-anadromous form. Genetic evidence from kokanee in the Fraser River drainage and Columbia River drainage shows that ancestors of the kokanee came from the lake-type sockeye. The data also suggests that the kokanee may have evolved back into a lake-type anadromous form