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1 ? 8 Index, Dissertation Index Abstracts International, Masters Abstracts International, and American Doctoral Dissertations provided 52 graduate degree documents based on native fish species names (all selected, APPENDIX II Table 3). Our final reference list comprised 416 citations published over a four-decade period, 1957 through 1997. HABITATS IN THE LOWER COLORADO RIVER -- Aquatic habitats of the lower Colorado River have been altered dramatically by human development of water resources (Fradkin 1981). Most striking among changes are those associated with construction and operation of high dams: creation of large lentic habitats represented by impoundments, and perennially clear, cold tailwaters in downstream river reaches. Also associated with dams and other river control structures are altered hydrologic (magnitude and timing of flows) and sediment transport (volume and source) regimes. These last parameters also have been profoundly influenced by land uses of tributary watersheds, such as domestic livestock grazing, groundwater withdrawal, mining, timber harvest, and urban development. Because of the over-riding effects of these by- products of human occupation, there are essentially no natural segments remaining along the mainstream lower Colorado River. The following discussion is generalized and intended to provide only an overview of the present-day lower Colorado River and its habitats. Although there are abundant anecdotal and narrative accounts of the lower river, there have been few quantitative studies of habitat per se, and fewer yet of habitat in context of fishes (see Minckley 1979, Hiebert and Grabowski 1985, 1987, and Marsh and Minckley 1985, 1987 as important exceptions). Additional detail also can be found in Anderson and Prichard 1951, Jonez and Sumner 1954, Hoffman and Jonez 1973, USBR 1976 and 1996, Priscu 1978, Paulson et al. 1980, Brown 1983, and USFWS 1997, and literature cited therein.