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The Virginia River roundtail chub, Gila robusta seminuda, was collected in the mainstream of the Virgin River downstream from Hurricane, Utah. It occurred in about one-half of all mainstream collections and comprised less than three percent of the fauna. The chub was generally found in runs and pools over sub- strates of sand and sediment in physically and chemically unmodified areas. The chub population has declined during the past 100 years due to increased agricultural and urban water use, decreased water quality, and introduction of exotic fishes. Alterations of the natural habitat of many Southwestern fishes have led to local and widespread extirpations. Interest in preserving certain endangered species has resulted in management policies and recla- mation efforts. Some species have been established in man-made re- fugia or have been transferred to habitats beyond their original range. For example, the Pahrump killifish, Empetrichthys latos, was trans- planted to a natural spring and a man-made pool before its original habitat (Manse Spring, Nye County, Nevada) was pumped dry (Anonymous 1977). In other instances efforts have been made to pre- serve the natural habitat. The increasing urban and agricultural de- mand for water is a threat to the continued survival of the native aquatic wildlife in the Southwest. The Virgin River is one of the few remaining unrestricted streams in the Southwest. The native ichthyo- fauna, though largely intact, has not been immune to the effects of 1 Research funds were provided by the U. S. Bureau of Sport Fisheries and Wild- life, the Western Interstate Commission for Higher Education, and the American |
