Sockeye salmon and more numerous eggs, better nest choice and ability to defend it, and the ability to bury eggs deeper and provide more protection. Females vary their breeding rate depending on the size of the courting male, mating more quickly with larger males. This increases the likelihood that larger males will displace attending, smaller males. Male sockeye salmon social status and greater reproductivity are directly associated with larger body size and more extreme body shapes; Larger bodies provide males with advantages when it comes to intrasexual competition and being selected for by females during reproduction. Males preferentially spawn with females who
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