Eagle trout, Oncorhynchus mykiss aquilarum, is a subspecies of Rainbow Trout endemic to Eagle Lake, in Lassen County, California. It is a type of trout, known for its ability to withstand high alkalinity.The Eagle trout name comes from its former exclusive-endemic Eagle Lake territory. The lake's trout population was thought to be extinct. A few were discovered in the lake in 1958, and the California Department of Fish and Game planted 5,000 of the trout in the lake. While formerly only in Eagle Lake, the Department of Fish and Game has transplanted the Eagle Lake trout into dozens of other lakes in California.