ABSTRACT
Before such drastic alteration to the watershed in the upper Colorado River Basin had occurred, it was a well-developed ecosystem characterized by a high level of endemism and a natural highly variable flow regime. For millions of years this ecosystem had been evolving to fit the physical stresses of this river and climate. During the middle of the last century human demands for power and water in the Southwestern United States prompted the ‘taming’ of this wild river system, which resulted in the construction of several dams and water diversions through out the Basin. Little was known about the affects these dams would have on native biota and the geological and hydrological characteristics of the rivers below.
Current research on the fish fauna of the Green River system is focused primarily on interspecific interactions, competition for resources, abundance and distribution of natives vs. non-natives, availability of quality habitat and any other information which may be relevant or insightful as to the mechanisms which may be responsible for the decline in the number of native fish in the Green River. This paper focuses on how anthropogenic and environmental factors coupled with the introduction of many non-native fish have affected native fish populations. In addition it discusses how the Serial Discontinuity Concept (Stanford and Ward 2001) predicts the distributions and proportions of populations and overall system biodiversity, to change due to the presence of the dam and compares that with the available information regarding current distributions and relative abundance of these fish.