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Page 30 ~ 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 roundtail chub, the threats to the bluehead sucker in these basins are similar: water diversions, non-natives, and oil exploration projects that affect water quality. Non- natives in the basin include brown trout, northern pike, smallmouth bass, white sucker, green ~ sunfish, red shiner, and walleye. Many higher elevation streams in the drainage that are suitable for bluehead sucker are also blue ribbon trout waters and thus are intended for sportfishing. Recent information shows a possible decline in numbers in the Duchesne River; however, more years of continuing surveys will help verify whether this is a true trend. Detailed information regarding the historical and current status of bluehead sucker and associated threats is found in ~ Table 2-4. Southeastern Region Bezzerides and Bestgen (2002) described bluehead sucker as abundant in the Colorado and ~ Dolores rivers and common in the Price, San Juan, and Dirty Devil rivers, though Valdez (1990) noted that bluehead sucker were rare in the mainstem Colorado -River from Lake Powell to Moab, UT in the late 1980's. Surveys for endangered. fishes in the San Juan River suggest that bluehead sucker are still relatively common there, though population information has not been quantified. Surveys suggest that bluehead sucker were historically abundant in the San Rafael ~ River drainage, but are now only rarely found in the drainage (C. Walker, Regional Biologist, Utah Division of Wildlife Resources, personal communication 2005). De-watering of stream segments as a result of residential and commercial water development is exacerbated by drought. Extensive diversion of instream flow can cause increases in water temperatures and declines in water quality throughout the entire stream length as overall water levels decline. In addition to ~ water quality, de-watering large stretches of rivers will segment migratory routes and provide direct benefit to riparian invasive species such as tamarisk, which further degrade the stream. Bluehead sucker in the Muddy Creek drainage show characteristics of both bluehead and mountain sucker (C. Walker, Regional Biologist, Utah Division of Wildlife Resources, personal communication 2005) indicating that introgression may be occurring as numbers decline. ~ Detailed information regarding the historical and current status of bluehead sucker and associated threats is found in Table 2-5. Southern Region Bluehead sucker were documented by McAda et al. (1977) in the Escalante River and thought to ~ be historically present in the Fremont River (Bezzerides and Bestgen 2002). They are still considered common in portions of these streams, though Fridell et al. (2004) and Morvilius and Fridell (2005) observed declines in many of the Escalante River tributaries (see Table 2-6). Mueller et al. (1998) did not observe the species in his surveys in the lower Escalante River; however, recent surveys by the Utah Division of Wildlife Resources in 2003 and 2004 revealed populations of all three species and very few non-natives in upper portions of this watershed