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Page 28 BLUEHEAD SUCKER Bluehead sucker are found in a variety of habitats. Adults prefer large, cool streams (20oC) with rocky substrates (Bestgen 2000, Sigler and Sigler 1996), but are also found in warm, small creeks with maximum water temperatures of 280C. They are thought to not do well in impoundments (Bezzerides and Bestgen 2002, Sigler and Sigler 1996). Bluehead sucker are opportunistic omnivores, consuming algae, detritus, plant debris, and occasionally aquatic invertebrates (Bestgen 2000, Osmundson 1999, Sigler and Sigler 1996). This species feeds in riflles or deep rocky pools (McAda 1977, Sigler and Sigler 1996). Bluehead sucker mature at two years of age and/or at 127 to 179 mm in length. Spawning occurs in shallow areas when water temperatures reach 15.60C. Time of spawning varies by elevation, i.e., spring and early summer at low elevations and warm water temperatures, and mid- to late summer at higher elevations and cooler temperatures (Sigler and Sigler 1996). Fecundity is related to length, body weight (Holden 1973), and water temperature (McAda 1977). A 38 to 44 cm female may produce over 20,000 eggs (Andreason 1973). Eggs hatch in seven days at water temperatures of 18 to 210C (Holden 1973). During spawning, bluehead sucker will compress to the bottom of the stream when disturbed and may be captured by hand (Sigler and Sigler 1996). Douglas and Douglas (2000) report that both indigenous bluehead and tlannelmouth sucker currently hybridize with invasive white sucker (Catostomus commersoni) in the Little Yampa Canyon region of the Yampa River, Colorado; white sucker also occur m the Green, Duchesne, and Fremont rivers in Utah. Douglas and Douglas (2000) also found two hybrids between tlannelmouth and bluehead sucker, which is rare elsewhere in the Colorado River Basin. Douglas and Douglas (2000) suggest backcrossing of fertile indigenous and invasive sucker hybrids as a mechanism perpetuating introgressed genes into the population. They also speculate that the species boundary between tlannelmouth and bluehead suckers could be compromised as a result. Hybridization between bluehead sucker and Rio Grande sucker (c. plebius) is thought to have produced the Zuni bluehead sucker (C.d. yarrowi), a unique subspecies found mainly in Rio Nutria, NM. BLUEHEAD SUCKER STATUS REVIEW General Bluehead sucker historically occurred in the Colorado River Basin, the Bonneville Basin in Utah, and the Snake River Basin in Idaho, Nevada, and Utah (Lee et al. 1980) (see Figure 2-7). In Utah, bluehead sucker in the San Juan River have been particularly well studied (Ryden 2001). Although bluehead sucker are considered common in the mainstem Green, San Rafael, Price, Duchesne, White, and San Juan rivers and abundant in the mainstem Colorado, Dolores, and Yampa rivers, they presently occupy only approximately 45% of their historical range in the Upper Colorado River basin (Bezzerides and Bestgen 2002). Recent declines of blue head sucker have occurred in the White River (Utah and Colorado) below Taylor Draw Dam and in the upper Green River (Bezzerides and Bestgen 2002, Holden and Stalnaker 1975) and in lower portions of many tributaries to the Escalante River (Fridell et a1. 2004; Morvilius and Fridell 2005). Northeastern Region Bluehead sucker are thought to be extirpated from a short stretch of the Green River below Flaming Gorge Dam, but common in the mainstem Green, Duchesne, and White rivers (Bezzerides and Bestgen 2002, Brunson 2001), including major tributaries such as the Strawberry River. Like the