Since the collapse of Mount Mazama due to a volcanic eruption formed Crater Lake, no fish inhabited the lake until William G. Steel decided to stock it in 1888 to allow for fishing. Regular stocking continued until 1941, when it was evident that the fish could maintain a stable population without outside interference. Six species of fish were originally stocked, but only two species have survived: Kokanee Salmon and Rainbow Trout with Kokanee being the most plentiful. Fishing in Crater Lake is promoted because the fish species are not indigenous to the lake.