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124 Swimming Against the Current were eventually agreed upon, and imposed certain restrictions on quantities and schedul- ing of (Jows (Harris et al. 1982). The 1948 Upper Colorado River Compact provided con- sumptive water rights for Arizona,California, and Nevada, and apportioned the remainder to the upper basin states of Colorado, New Mexico, Utah, and Wyoming. Division of water among the states cleared the way for development of several major water projects in the upper basin. In 1956 the Colorado River Storage Project Act authorized construc- tion of large main-stem dams on the upper Colorado and its tributaries. The project in- cluded six reservoirs: Blue Mesa, Crystal, Flaming Gorge, Morrow Point, Navajo, and Powell. The last to be constructed, Lake Pow- ell, was completed in 1962. and filled by 1980. In the early 1960s the endangered Col- orado River fishes were considered undesir- able "rough" fish by conservation agencies. As a result, the largest rotenone treatment ever applied in the United States until that time was conducted to remove them and other un- wanted species such as common carp (Cypri- nus carpio) from the Green River above Flam- ing Gorge Dam. The goal was to create a SpOrt fishery for introduced salmonids (Binns 1965; Holden, this volume, chap. 3). Before the rote- none could be completely detoxified, it con- tinued downstream into Dinosaur National Monument (NM), Reductions in native fish numbers were greatest in the uppermost part of the monument, at the Gates of Lodore, and diminished as the chemical moved down- stream. Although the poison adversely af- fected native fishes and invertebrates, the eventual ecological changes to riverine envi- ronments caused by Flaming Gorge Dam were believed more important in ultimately re- ducing their populations (Holden, this vol- ume, chap. 3). The Colorado River Storage Project dams and reservoirs, along with private and local water developments, all combined to alter nat- ural flow, water temperature, and sediment transport in much of the upper basin. Peak spring flows were diminished and low stable flows at other times of year were elevated by reservoir releases that changed the natural hy- drograph (Vanicek et al. 1970). These projects also resulted in direct losses of stream habitat through inundation by reservoirs and block- age of migration routes. Concurrently, various non-native fishes were intentionally or accidentally introduced. [n 1976 the Colorado River Wildlife Council listed twenty species (40%) as nati~e to the system and thirty (60%) as introduced (W M. Richardson 1976). At the same time, Hol- den and Stalnaker (1975a) reported ten na- tive fishes (34.5"10) and nineteen non-native (65.5"10) in the upper basin. By 1982. the non- native species had increased to 76% of the fifty-five fishes known to occur in the upper basin (Tyus et al. 1982a). [t is generally be- lieved that predation and competition by in- troduced fishes are major factors adversely af- fecting the endemic species. Competition for Water Drought in the late 1800s followed by pro- longed flooding in the early 1900S in the lower Colorado River basin stimulated de- mands for control of the Colorado River (Fradkin 1984). Construction of Roosevelt Dam on the Salt River in 1913 and Hoover Dam in 1935, followed by other main-stem dams, changed much of the free-flowing river to a lacustrine environment. Stream flow and temperature regimes in the remaining river were greatly altered. These events were closely followed by declines in native fishes in the lower basin. Colorado squawfish were extir- pated, and bony tails, humpback chubs, and razorback suckers were drastically reduced in numbers and distribution. Only large, old bony tails and razorback suckers were still found in reservoirs of the lower basin by the