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ECOLOGY AND CONSERVATION OF NATIVE FISHES IN THE UPPER COLORADO RIvER BASIN 169 historically found in the upper Colorado, Green, and San Juan river drainages (Bezzerides and Bestgen 2002). It currently occupies about 50% of historic upper basin habitat where it persists as eight populations in the upper Colorado, Green, and San Juan rivers and their tributaries, includ- ing the Escalante, Fremont, San Rafael, Price, Duchesne, White, Yampa, Little Snake, Animas, and La Plata rivers (Bezzerides and Bestgen 2002). It is found in the upper Colorado River from Glenwood Springs, Colorado, to Lake Powell; the Green River from Daniel, Wyoming, to the Colo- rado River confluence (except Flaming Gorge and Fonrenelle reservoirs); and the San Juan River from Bloomfield, New Mexico, to Lake Powell. Tempera- ture range of flannelmouth sucker is 10-270C (Sublette et al. 1990). Flannelmouth sucker typically occupy pools, eddies, and deep runs and may congregate to feed at the base of cobble riffles (McAda et al. 1980; Valdez et al. 1982a; Sublette et al. 1990). Larvae and young use low-velocity habitats along shallow shorelines and backwaters, eddies, and side chan- nels over silt substrates (Banks 1964; Minckley 1973; McAda 1977; Snyder and Muth 2004; Childs et al. 1998; Gido and Propst 1999). Juve- niles use deep shorelines and shallow gravel/ cobble riffles, and adults are common over rocky substrates (Holden and Stalnaker 1975a; McAda et al. 1980). Flannelmouth sucker were found in newly formed impoundments, such as Flaming Gorge Reservoir, Lake Powell, and Kenny Reservoir, but declined dramatically from predation, and repro- ductive and recruitment failure (Baxter and Stone 1995; Binns 1967; Minckley 1973; McAda 1977; Chart 1987). It is a moderately migratory, potadromollS species with long-distance movements usually associated with spawning (Vanicek 1967; Holden 1973; Holden and Crist 1981; Chart and Bergersen 1992; Douglas and Marsh 1998; Beyers et al. 2001). Movements of up to 62 km were re- ported between the Price River and the Green River in 1997 and 1998 (Cavalli 1999). Fecun- dity is 4,000-33,000 eggs per female (McAda 1977; McAda and Wydoski 1980), and spawning in the upper basin is in May and June at water temperatures of 16-18.50C (Holden 1973; Minckley 1973; Snyder and Muth 2004). Adhe- sive eggs are deposited over sand and gravel bars, they incubate 6-7 d at 15.5-17.80C, and larvae hatch at 10-11 mm TL (Snyder and Muth 2004). Larvae emerge from cobble substrates and are trans- ported downstream by river currents to low-veloc- ity, sheltered, shoreline nursery habitats (Childs et al. 1998) with greatest drift densities at night and along shorelines (Valdez et al. 1985). Flannelmouth sucker are omnivorous and consume seeds, plant debris, algae, aquatic invertebrates, phytoplankton, and organic detritus (Minckley 1973; Grabowski and Hiebert 1989; Muth and Snyder 1995). B/uehead Sucker Bluehead sucker is a small to medium size fish (300- 450 mm TL) with a short, broad, bluish head. The sucker mouth is subterminal with strong jaws and cartilaginous scraping ridges, more pronounced on the maxillary. The body is elongate and tapers to a caudal peduncle of varying thickness, generally more robust and deep in fish from tributaries and low- velocity regions than the more slender, streamlined form from mainstream habitats. Bluehead sucker hy- bridizes with native flannelmouth sucker, rawrback sucker, and mountain sucker, and nonnative white sucker (Hubbs et al. 1942; Smith 1966; Holden and Stalnaker 1975a, 1975b; Holden and Crist 1981). The species does not currently receive fed- eral protection under the ESA, but is one of three species included in a conservation agreement among six western states (Colorado Fish and Wildlife Coun- cil2004). In the upper basin, bluehead sucker was found up to about 2,300 m elevation in the upper Colo- rado, Green, and Sanjuan river drainages (Smith 1966; Sublette et al. 1990; Baxter and Stone 1995). It currently occurs as 10 populations in ap- proximately 45% of historic upper basin habitat (Bezzerides and Bestgen 2002). Reservoir inunda- tion and cold releases from dams account for most losses of abundance and distribution. Some popu- lations have been fragmented or isolated by dams and reservoirs, including the upper Green River above Flaming Gorge Reservoir, Gunnison River above the Aspinall Unit, and White River above Taylor Draw Dam (Martinez et al. 1994). Bluehead sucker feed in cobble/gravel riffles