North American beaver (Castor canadensis) are now prevalent on Trout Creek, and have built over 30 dams from the bridge on Donner Pass Road to the Truckee River. Beaver were re-introduced to the Tahoe Basin by the California Department of Fish and Game (CDFG) and the U. S. Forest Service between 1934 and 1949 in order to prevent stream degradation and to promote wetland restoration. That beaver were once native to the area is supported by the fact that the Washo have a word for beaver, c'imhélhel and the northern Paiute of Walker Lake, Honey Lake and Pyramid Lake have a word for beaver su-i'-tu-ti-kut'-teh. When Stephen Powers visited the northern Paiute to collect Indian materials for the Smithsonian Institution in preparation for the Centennial Exhibition of 1876, he reported that the northern Paiute wrapped their hair in strips of beaver fur, made medicine from parts of beaver and that their creation legend included beaver. In addition, fur trapper Stephen Hall Meek set his traps on the Truckee River in 1833, which strongly suggests that he saw beaver or beaver sign. The presence of beaver dams has been shown to either increase the number of fish, their size, or both, in a study of brook, rainbow and brown trout in nearby Sagehen Creek, which flows into the Little Truckee River at an altitude of and is a stream typical of the eastern slope of the northern Sierra Nevada. Not only have aspen and cottonwood survived ongoing beaver colonization but a recent study of ten Tahoe streams utilizing aerial multispectral videography, including Trout Creek and Cold Creek, has shown that deciduous, thick and thin herbaceous vegetation has increased near beaver dams, whereas coniferous trees are decreased. Benefits of beaver dams include removal of sediment and excessive pollutants travelling downstream, which improves water clarity, which was shown to worsen when beaver dams were recently removed in nearby Taylor Creek and Ward Creek. Flooding from beaver dams is relatively inexpensively controlled with flow devices.