Undergraduate Abstract

ABSTRACT

The Virgin River originates in southwestern Utah and joins the Colorado River in southern Nevada where it flows into the Overton Arm of Lake Mead. Analysis of a considerable database on native fishes collected over the past 17 years, supplemented by historical records, reveals reductions in both distribution and abundance of the native fish community. Following construction of Hoover Dam, Lake Mead flooded the lower 25 miles of the Virgin River, eliminating the native fish community in the 1930's. Reservoir construction, development of trout fisheries, and cattle grazing, depleted native fish communities in tributary streams during the 1960's and 1970's. The middle mainstream fish fauna was most severely affected during the 1980's following upstream invasion by the introduced red shiner and construction of a 45,000 acre-foot off stream reservoir. The native fish community of the Virgin River Drainage maintains relatively natural abundance today only in Zion National Park and for a short distance downstream, and in a segment of the Santa Clara River above Gunlock Reservoir. Water development plans for the future threaten the fish community in those areas. Federal Reserved Water Rights, management of endangered species, sport fish management, irrigation rights, and pressure to provide water for urban growth place conflicting demands on the Virgin River and highlight ethical dilemmas of a human population faced with adjusting to a world with limits.