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be able to compare concentrations in muscle tissue with whole body tissue, estimates have been <br /> calculated using the Model B regression equation and the intercept developed for Northern <br /> pikeminnow presented in Peterson et al. (2005), as explained earlier in the Environmental <br /> Baseline section. Using this equation, a concentration of 0.2 µg/g WW in whole body fish <br /> translates to a value of 0.31 µg/g WW in muscle tissue. <br /> More recently, after an examination of numerous mercury studies, Sandheinrich and Wiener <br /> (2011) stated that freshwater fish begin to exhibit sub-lethal, yet detectible negative effects <br /> through changes in biochemical processes, damage to cells and tissues, and reduced reproduction <br /> at methylmercury concentrations of about 0.5-1.2 µg/g WW mercury in muscle tissue (0.3-0.7 <br /> µg/g WW mercury in whole body fish). They state that nearly all mercury in fish is in the form <br /> of methylmercury, as this is the form that bioaccumulates and biomagnifies up through the food <br /> chain. Note also that the EPA human health consumption advisory is 0.3 µg/g/day of mercury <br /> (WW) in fish tissue (EPA 2001). <br /> As stated in the Environmental Baseline section above,we have historic information on the <br /> mercury concentrations found in Colorado pikeminnow tissue that were collected in the Yampa <br /> and White Rivers,but are lacking this historic data for the other three endangered fish. The <br /> mercury concentrations reported by Osmundson and Lusk(2012)ranged from 0.39 to 0.58 µg/g <br /> with a mean level of 0.49 µg/g in muscle plug samples taken from Colorado pikeminnow in the <br /> Yampa River(9 fish sampled 2008-2009). Prior to that,muscle plug samples taken from <br /> Colorado pikeminnow in the Yampa River in 2006 had concentrations of mercury between 0.42 <br /> and 0.68 µg/g (CDPHE 2015). Earlier still, Osmundson and Lusk(2012)reported on the <br /> mercury concentrations in muscle plugs taken from archival pikeminnow collected in the Yampa <br /> River during 1964-1966,which measured 0.41-0.88 µg/g total mercury. Most of these mercury <br /> concentrations are above the effects threshold suggested by Beckvar et al. (2005) (muscle tissue <br /> equivalent) at 0.31 µg/g, but are below or at the concentrations identified by Sandheinrich and <br /> Wiener(2011)where negative effects would become detectible (0.5-1.2 µg/g). <br /> Osmundson and Lusk(2012) found that mercury concentrations in White River Colorado <br /> pikeminnow were higher than concentrations in Colorado pikeminnow in other river segments of <br /> critical habitat. They found a mean muscle tissue concentration of 0.95 µg/g in White River <br /> pikeminnow with a range of 0.43 to 1.83 µg/g (Osmundson and Lusk 2012). Colorado <br /> pikeminnow taken from the White River over 20 years earlier was reported at 0.5 to 1.75 µg/g of <br /> mercury in muscle tissue WW by Krueger(1988) (after conversion from whole body dry <br /> weight). The measured mercury concentrations indicate that some individuals of this endangered <br /> fish species with higher mercury concentrations have exceeded toxicity measurement thresholds <br /> and have mercury concentrations at a level where sub-lethal harmful effects become measurable <br /> in many other fish species (Sandheinrich and Wiener 2011). <br /> Based on these results,we expect that some Colorado pikeminnow in the action area may already <br /> be experiencing chronic, sub-lethal harmful effects, such as potentially reduced reproductive <br /> success or reduced vigor, from elevated mercury concentrations. It should be noted,however, <br /> that piscivorous fish living in fresh waters in the midwestern and eastern United States, and some <br /> waters in the western United States contaminated by mining activities, have been reported to <br /> contain concentrations exceeding 1.0 µg/g WW in muscle tissue (Sandheinrich and Wiener <br /> 50 <br />