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Page 36 FLANNELMOUTH SUCKER Flannelmouth sucker reside in mainstem and tributary streams. Elements of flannelmouth sucker habitat include 0.9 to 6.1 m deep murky pools with little to no vegetation and deep runs and riffles (Bezzerides and Bestgen 2002, McAda 1977, Sigler and Sigler 1996). Preferred substrates consist of gravel, rock, sand, or mud (McAda 1977, Sigler and Sigler 1996). Flannelmouth sucker partition habitat use by life stage, with young fish occupying quiet, shallow riffles and near-shore eddies, and adults occupying deep riffles and runs. Flannelmouth sucker do not prosper in impoundments (Bezzerides and Bestgen 2002, McAda 1977, Sigler and Sigler 1996), though one introduction during the 1970's in Lake Havasu in the lower Colorado River Basin continues to persist (Mueller and Wydoski 2003). Flannelmouth sucker are opportunistic, benthic omnivores consuming algae, detritus, plant debris, and aquatic invertebrates (Bezzerides and Bestgen 2002, McAda 1977, Osmundson 1999, Sigler and Sigler 1996). Food consumed depends on availability, age class, and time of season (McAda 1977, Sigler and Sigler 1996). Flannelmouth sucker mature at four or five years of age; males mature earliest (McAda 1977, Sigler and Sigler 1996). Females ripen at water temperatures of lOoC, whereas males ripen earlier in the spring (6.1 to 6.70C) and remain fertile for a longer period of time (McAda 1977, Sigler and Sigler 1996). Seasonal migrations are made in the spring to suitable spawning habitat (Sigler and Sigler 1996, Suttkus and Clemmer 1979). McKinney et al. (1999; see also Bergersen 1992, Chart 1987, Chart and Bergersen 1987) documented long-range movements (ca. 98-231 kIn) among adult and sub-adult fish, although the roles these movements (and obstructions to such, i.e., dams) play in the life history of the fish are unclear. Many researchers suspect that flannelmouth sucker return to natal tributaries for the purpose of spawning (Snyder and Muth 1990; Weiss et al. 1998). Populations spawn for two to five weeks over gravel substrates. A female will produce 9,000 to 23,000 adhesive, demersal eggs. After fertilization, the eggs sink to the bottom of the stream and attach to substrate or drift between crevices (Sigler and Sigler 1996). FLANNELMOUTH SUCKER STATUS REVIEW General Historical literature suggests that flannelmouth sucker 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 have been greatly reduced in the lower Colorado River Basin, but are still widespread in the upper basin (Bezzerides and Bestgen 2002). They are thought to remain in at least 50% of their historical range above Glen Canyon Dam (Bezzerides and Bestgen 2002). There are extant populations in the mainstem Colorado and in tributaries in the Grand Canyon reach and in the Virgin River in Utah, Arizona, and Nevada (see Figure 2-8). Of the historical flannelmouth sucker sites in Utah, the species has only been extirpated from sites near Flaming Gorge Dam (Vanicek et al. 1970). Flannelmouth sucker continue to be documented at all other sites. Hybridization with nonnative white sucker is thought to be an increasing threat. White sucker are commonly seen in the Green River and have been seen occasionally in smaller tributaries of the Green and Colorado rivers. As the range of the white sucker increases, it is thought that the range of the flannelmouth sucker will decrease, as hybridization between the two species is prevalent (Anderson and Stewart 2000, Bestgen and Crist 2000, Holden and Crist 1981, Holden and Stalnaker 1975). Northeastern Region