Geohydrologic reconnaissance of Lake Mead National Recreation Area; Virgin River, Nevada, to Grand Wash Cliffs, Arizona

Artifacts from 24 chipping stations and a lithic scatter from the Lake Mead National Recreation Area, Nevada were analyzed by refitting conjoinable flakes to original cores. Artifacts represented debitage from the initial reduction of locally-available low-quality chalcedony nodules for the eventual production of flake tools. The refitting analysis allowed the debitage to be divided into four patterns that roughly correlate with variation in the quality of the raw material. All result from the same strategy of reduction aimed at producing as many usable flakes as possible from low-quality material. Such relatively unproductive sites are rarely studied in detail because they require intensive analysis, but were probably an important part of prehistoric resource systems.

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Historical Changes in Large River Fish Assemblages of the Americas

Historical Changes in Large River Fish Assemblages of the Americas ◽

10.47886/9781888569728.ch7 ◽

2005 ◽

Keyword(s):

Native Species ◽

Fish Assemblages ◽

Fish Fauna ◽

River System ◽

Endangered Species Act ◽

Large River ◽

Main Stem ◽

Lake Mead ◽

Virgin River ◽

Native Fishes

Abstract.—The Virgin–Moapa River system supports nine native fish species or subspecies, of which five are endemic. Woundfin Plagopterus argentissimus and Virgin River chub Gila seminuda are endemic to the main-stem Virgin River, whereas cooler and clearer tributaries are home to the Virgin spinedace Lepidomeda mollispinis. Moapa dace Moapa coriacea and Moapa White River springfish Crenichthys baileyi moapae are found in thermal springs that form the Moapa River, and Moapa speckled dace Rhinichthys osculus moapae is generally found below the springs in cooler waters. The agricultural heritage of the Virgin–Moapa River system resulted in numerous diversions that increased as municipal demands rose in recent years. In the early 1900s, trout were introduced into some of the cooler tributary streams, adversely affecting Virgin spinedace and other native species. The creation of Lake Mead in 1935 inundated the lower 80 km of the Virgin River and the lower 8 km of the Moapa River. Shortly thereafter, nonnative fishes invaded upstream from Lake Mead, and these species have continued to proliferate. Growing communities continue to compete for Virgin River water. These anthropogenic changes have reduced distribution and abundance of the native Virgin–Moapa River system fish fauna. The woundfin, Virgin River chub, and Moapa dace are listed as endangered, and the Virgin spinedace has been proposed for listing. In this paper we document how the abundance of these species has declined since the Endangered Species Act of 1973. Currently, there is no strong main-stem refugium for the Virgin River native fishes, tributary refugia continue to be shortened, and the Moapa River native fishes continue to be jeopardized. Recovery efforts for the listed and other native fishes, especially in the Virgin River, have monitored the declines, but have not implemented recovery actions effective in reversing them.

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