The trout have been planted in streams for many years, but their populations have grown so large that scientists believe they re simply running out of food in streams. Scientists finally realized that the fish are regenerating naturally and that the plantings were overpopulating streams. As the habitat for the trout declines, the populations of frogs have disappeared in many streams. This is true on the Eastern Sierra as well as the Tahoe area. Scientists do not know if the trout are eating the frogs or if the decline of trout habitat is also affecting the frog population.
Some scientists believe the two populations are unrelated.
The federal government has cut back the planting of fingerlings and study continues on the dwindling frog population. Following is information on trout and yellow-legged frogs submitted by Roland A. Knapp , of the Sierra Nevada Aquatic Research Laboratory at the University of California. The mountain yellow-legged frog was once the most common amphibian in the high elevation portions of the Sierra Nevada, where it inhabited the many fishless lakes, ponds, streams, and marshes. Today, this frog is one of the rarest amphibians in the Sierra Nevada, and because of the severity of its decline is likely to soon be listed as endangered under the federal Endangered Species Act. Contaminants drifting out of the Central Valley and disease may also play significant roles.