Sockeye salmon natural selection against large bodies. Populations with higher levels of predation tend to evolve smaller body size. Without the threat of predation, salmon that breed early in the season live longer than those that breed late in the season. Other ecological factors like stranding effect select for smaller body size in sockeye salmon when present in a habitat. Stranding is when salmon swim into dry land or shallow water during their migration for spawning and die from suffocation. In fact, studies show that the Sockeye salmon with the largest bodies are most susceptible to stranding mortality. Reproduction is marked by
Sockeye salmon Resources Commission in an attempt to establish the species as a forage fish for other predator fishes in the lake. This stock has remained and become a favorite target for anglers. In Japan, a landlocked variety termed black kokanee, or ""kunimasu"" in Japanese, was deemed to be extinct after 1940, when a hydroelectric project made its native lake in northern Akita Prefecture more acidic. The species seems to have been saved by transferring eggs to Saiko Lake, 500 kilometers to the south, however. This fish has been treated as a subspecies of sockeye "Oncorhynchus nerka kawamurae", or even an independent