Man and the Changing Fish Fauna of the American Southwest
t,P • PAPERS OF THE MICHIGAN ACADEMY OF SCIENCE, ARTS, AND LETTERS VOL. XLVI, 1961 GS.110 4.Marrma) • Af.4,114.-aiLsk, 71 ici4,1 MAN AND THE CHANGING FISH FAUNA OF •THE AMERICAN SOUTHWEST' . ROBERT RUSH MILLER Museum of Zool9gy, The University of Michigan TEE past 100 years have witnessed drastia changes in the rivers of Western North America and in their fish faunas. Deterioration of stream flow has greatly shrunk the ranges of many species, and other species have been denied access to large segments of their original distribution by the construction of barrier dams. Profound modifica- tion of pristine environments has restricted habitable waters, and the introduction and establishment of a host of exotics have brought about replacement as well as reduction of native forms through com- petition, predation, and hybridization. Some species and subspecies ave become extinct, and many others are endangered (Matthiessen, 959). These changes have been particularly marked in areas of ricted water supply such as characterize the arid Southwest ,;(Fig: 1 . Much of this region is embraced by the Basin and Range ProvinCe *: (Fenneman; 1931, pl. I), including the Great Basin, Sonoran Desert; - and the Chihuahuan Desert of northern Mexico. Only about 100 species of strictly fresh-water fishes are known west of the Rocky Mountains and north of Mexico—a depauperate - fauna characterized by relicts, monotypic genera, and much regional The initial version of this paper was presented at the Fifth Annual Sym- posium on Systematics, Missouri Botanical Garden, St. Louis, on October 25, , 1958, under the general subject "Taxonomic Consequences of Man's Activities." Yield work has been generously supported by the Horace H.
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