2010-11-22_REVISION - M2009023 (7)

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100-year floodplain of the Colorado pikeminnow's historical range in the following section of the San Juan River Basin (59 F.R. 13374) (USFWS 1993 and 1994). New Mexico, San Juan County; and Utah San Juan Count. The San Juan River from the State Route 371 Bridge in T. 29 N., R. 13 W., section 17 to Neskahai Canyon up to the full pool elevation in the San Juan arm of Lake Powell in T. 41 S., R. 11 E., section 26. The Service has identified water, physical habitat, and the biological environment as the primary constituent elements of critical habitat. This includes a quantity of water of sufficient quality that is delivered to a specific location in accordance with a hydrologic regime that is required for the particular life stage for each species. The physical habitat includes areas of the Colorado River system that are inhabited or potentially habitable for use in spawning and feeding, as a nursery, or serve as corridors between these areas. In addition, oxbows; backwaters, and other areas in the I00-year floodplain, when inundated, provide access to spawning, nursery, feeding, and rearing habitats. Food supply, predation and competition are important elements of the biological environment. / , Status and Distribution Based on early fish collection records, archaeological finds, and other observations, the Colorado pikeminnow was once found throughout warrnwater reaches of the entire Colorado River Basin down to the Gulf of California, and including reaches of the Upper Colorado River and its major tributaries, the Green River and its major tributaries, the San Juan River and some of its tributaries, and the Gila River system in Arizona (Seethaler 1978). Colorado pikeminnow apparently were never found in colder, headwater areas. Seethaler (1978) indicates that the species was abundant in suitable habitat throughout the entire Colorado River Basin prior to the 1850s. By the 1970s they were extirpated from the entire lower basin (downstream of Glen Canyon Dam) and from portions of the upper basin as a result of major alterations to the riverine environment. Having lost some 75-80 percent of its former range, the Colorado pikeminnow was federally listed as an endangered species in 1967 (Miller 1961, Moyle 1976, Tyus 1991, Osmundson and Burnham 1998). Platania and Young (1989) summarized historic fish collections in the San Juan River drainage which indicate that Colorado pikeminnow once inhabited reaches above what is now the Navajo Dam and Reservoir near Rosa, New Mexico. Since closure of the dam in 1962 and the accompanying fish eradication program, physical changes (flow, temperature, and the impoundment of water) associated with operation and presence of the Navajo Project have eliminated wild Colorado pikeminnow in the upper San Juan River, both upstream of Navajo Dam as well as at least 25 river miles downstream of the darn. Habitat has been significantly degraded to where it impairs the essential functions of Colorado pikeminnow such as reproduction and recruitment into the adult population. Major declines in Colorado pikeminnow populations occurred during the dam-building era of the 1930s through the 1960s, Behnke and Benson (1983) summarized the decline of the natural ecosystem, pointing out that dams, impoundments, and water use practices drastically modified the river's natural hydrology and channel characteristics throughout the Colorado River Basin. Dams on the mainstem fragmented the natural continuum of the river ecosystem into a series of disjunct segments, blocking native fish migrations, reducing water temperatures downstream of 5