2022-12-19_GENERAL DOCUMENTS - C1981010

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native suckers hybridized with nonnative suckers would threaten gene pools of wild native or endangered suckers. McDonald et al. (2008)revealed that hybridization of native bluehead (Catostomus discobolus) and flannelmouth (Catostomus latipinnis) suckers with the nonnative white sucker(Catostomus commersonii) increased introgression between the native suckers. This mechanism could ultimately pose an increased threat of hybridization for razorback sucker (USFWS 2002b). Selenium, a trace element, is a natural component of coal and soils in many areas of the western United States and can be released to the environment by the irrigation of selenium-rich soils and the burning of coal in power plants with subsequent emissions to air and deposition to land and surface water. Contributions from anthropogenic sources have increased with the increases of world population, energy demand, and expansion of irrigated agriculture (Mayer et al. 2010). Selenium can enter surface waters through erosion, leaching, and runoff. Excess selenium in fish have been shown to have a wide range of adverse effects including mortality,reproductive impairment, effects on growth, and developmental and teratogenic effects including edema and finfold, craniofacial, and skeletal deformities (Lemly 2002, Hamilton et al. 2004; Holm et al 2005). Excess dietary selenium causes elevated selenium concentrations to be deposited into developing eggs,particularly the yolk(Buhl and Hamilton 2000, Lemly 2002, Janz 2010). If concentrations in the egg are sufficiently high, developing proteins and enzymes become dysfunctional, leading to embryo deformation and a higher risk of mortality. Embryos that do survive, hatch, and grow may experience an elevated risk of predation as small fish. Of all the endangered fish in the Colorado River system, concern regarding elevated selenium levels is greatest for the razorback sucker(Hamilton et al. 2002; Osmundson et al. 2010). Hamilton (1999)hypothesized that historic selenium contamination of the upper and lower Colorado River basins contributed to the decline of these endangered fish by affecting their overall reproductive success, including loss of eggs and larvae. Selenium concentrations in whole-body fish in the Colorado River Basin have been among the highest in the nation (Hamilton 1999). Several Department of the Interior National Irrigation Water Quality Program (NIWQP) studies in the Colorado River Basin have reported elevated levels of selenium in water, sediment, and biota, including fish (Hamilton 1999). In the NIWQP studies of 25 areas in the 15 western states, the middle Green River ranked P for the highest median water concentration of selenium, Ist for sediment, and Ist for fish, and 141h for birds. The Gunnison River Basin/Grand Valley ranked 41h for the highest median water concentration of selenium, 2nd for sediment, 71h for fish, and Is'for birds (Engberg, 1998, as seen in Hamilton 1999). Unlike the Green, Gunnison, and Colorado Rivers,high selenium levels have not been reported in the Yampa and White Rivers (see section 3.3 Contaminants in the Action Area below for further discussion). While selenium has been more the focus of contaminants research involving the razorback sucker,mercury, which can pose a threat to any animal species, could also pose a threat at elevated concentrations. Because the razorback sucker is not a top predator, as is the Colorado pikeminnow,we expect mercury bioaccumulation (through prey)to pose less of a problem for this species. To summarize,razorback sucker habitat loss and degradation from dams and diversions constructed decades ago posed some of the early, primary impacts to the species. Most of the long-term impacts from these structures continue and are unlikely to change significantly in the 22