Between 1920 and 1975 stocks of several other varieties of rainbow trout and cutthroat trout were introduced into Lake Crescent. During the 1970s it was possible to catch trout of almost all shapes, sizes and colours without being certain that any individual was either the native rainbow or cutthroat. Doubts were expressed that these native strains could ever have survived in a pure state. However, research carried out in the early 1980s by Bryan Pierce of the Colorado State University demonstrated that both species of wild trout have survived in the lake, genetically intact. These two very close species coexisted without interbreeding.
Old reports demonstrate that the two had quite different ecologies in the lake.
Some degree of competition was further avoided by the young cutthroats remaining in their natal streams for the first two years of life, while the rainbow trout fry entered the lake immediately after leaving the redds.