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6 <br />pikeminnow apparently were never found in colder, headwater areas. <br />Seethaler (1978) indicates that the species was abundant in suitable <br />habitat throughout the entire Colorado River Basin prior to the <br />1850'x. No historic records exist that would indicate how far <br />upstream Colorado pikeminnow once occurred in the Colorado River. The <br />only reliable account of the species occurring upstream. of the Price <br />Stubb Dam near Palisade, Colorado is from a Service biologist who <br />reports having captured Colorado pikeminnow 2-3 miles up Plateau Creek <br />while angling there around 1960 (Robert Burdick pers. com.). <br />Critical habitat was designated in 1994 within the 100-year floodplain <br />of the Colorado pikeminnow's historical range in the following area of <br />the Upper Colorado River (59 F.R. 13374). <br />Colorado Mesa nd .arf i 1 d o m ; a : and T ah Crsnd 4ayn1uan . <br />~yll.~ and _arf; l d o ,n ; c . The Colorado River ,snd its 100-year <br />floodplain from the Colorado River Bridge at exit 90 north off <br />Interstate 70 in T. 6 S., R. 93 W., section 16 (6t:h Principal <br />Meridian) to North Wash, including the Dirty Devil arm of Lake <br />Powell up to the full pool elevation, in T. 33 5., R. 14 E., <br />section 29 (Salt Lake Meridian). <br />The Service has identified water, physical habitat, and the biological <br />environment as the primary constituent elements of critical habitat. <br />This includes a quantity of water of sufficient quality that is <br />delivered to a specific location in accordance with a 1-,ydrologic <br />regime that is required for the particular life stage f'or each <br />species. The physical habitat includes areas of the Colorado River <br />system that are inhabited or potentially habitable for use in spawning <br />and feeding, as a nursery, or serve as corridors between these areas. <br />In addition, oxbows, backwaters, and other areas in the: 100-year <br />floodplain, when inundated, provide access to spawning, nursery, <br />feeding, and rearing habitats. Food supply, predation and competition <br />are important elements of the biological environment. <br />Colorado pikeminnow were historically distributed throughout warmwater <br />reaches of the Colorado River Basin from Wyoming and Colorado south to <br />the Gulf of California. By the 1970s they were extirpated from the <br />entire lower basin (downstream of Glen Canyon Dam) and from portions <br />of the upper basin as a result of major alterations to the riverine <br />environment. Raving lost some 75-80 percent of its fox~ner range, the <br />Colorado pikeminnow was Federally listed as an endangex-ed species in <br />1967 (Miller 1961, Moyle 1976, Tyus 1991, Oamundson and Burnham 1998). <br />Colorado pikeminnow are presently restricted to the Upper Colorado <br />River Basin and inhabit warmwater reaches of the Colorado, Green, and <br />San Juan Rivers and associated tributaries. The species inhabits <br />about 350 miles of the main stem Green River from its confluence with <br />