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Page 22 and Arizona was recently divided into three species, G. robusta, G. intermedia, and G. nigra through genetic analysis (Minckley and DeMarais 1990). Additional investigation of these relationships and resulting offspring is needed and may affect future conservation and management actions for roundtail chub and other Gila species. The Virgin chub (G. seminuda) found in the Virgin River has been historically treated as a subspecies of roundtail chub (Maddux et al. 1995) and is thought to have originated through hybridization between the bonytail and the Colorado roundtail chub (Maddux et al. 1995, Sigler and Sigler 1996 and references therein). In 1993, taxonomic revisions were accepted, and the Virgin chub was asserted species status as G, seminuda (Maddux et al. 1995). It is currently listed as endangered under the federal Endangered Species Act. Roundtail chub presently exist in the United States only in the Gila River Basin, the Little Colorado . River Basin, the Bill Williams River Basin, and the Upper Colorado River Basin, including the Green River Basin. Lee et al. (1980) also recorded occurrences in northern Mexico, which was anecdotally confirmed by personal communications in 2001 with S. Contreras-Balderas (Bioconservacion A.C., Monterrey, Nuevo Leon) and A. Varela-Romero (Universidad de Sonora, Hermasillo). In Utah, roundtail chub occur in the Green and Colorado rivers and major tributaries of the two. Historically, roundtail chub were found in all of the state's major drainages, though abundance information was not recorded (see Figure 2-6) (Utah Division of Wildlife Resources 2001). ROUNDTAIL CHUB STATUS REVIEW General Historical literature suggests that roundtail chub were common to all parts of the Colorado River Basin up to the 1960's (Jordan and Evermann 1902, Minckley 1973, Sigler and Miller 1963). They are believed to have occurred in most faster flowing rivers and streams below 2,300 meters elevation (Bezzerides and Bestgen 2002). While they continue to occupy a number of rivers and streams in the upper basin, declines in numbers and relative abundance have been observed in many of these locations (Bezzerides and Bestgen 2002, Brunson and Christopherson 2003, Platania 1990). Northeastern Region Roundtail chub abundance in the mainstem Green River and associated tributaries has declined since the installation of multiple water development projects beginning in 1902 (Bezzerides and Bestgen 2002). In addition to water development, the introduction of nonnative predators and competitors over the same time period has proven to be detrimental to the roundtail chub (Bezzerides and Bestgen 2002) as have the presence of oil exploration projects within the drainage. Roundtail chub were described as abundant in the Duchesne River as late as 1975 (Holden and Stalnaker 1975) and common in 1982 (Tyus et al. 1982), but have since declined in numbers (Brunson and Christopherson 2003). In the White River, oil exploration projects and the presence of non-natives are the largest problems. Roundtail chub were considered abundant in the White River in 1975 (Holden and Stalnaker 1975), but only relatively common in 1981 (11 % of catch; Lanigan and Berry 1981) and 1982 (8-10% of catch; Miller et al. 1982). Flaming Gorge Dam is thought to have impacted roundtail chub at three sites: Willow Creek, Little Hole, and Brown's Park. Roundtail chub were found at these locations in 1962, but not in 1964, 1965, 19661 or 2004 (UDWR unpublished).