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In addition, as discussed in the Baseline section above,the decline in Colorado pikeminnow <br /> numbers within the Yampa River has been more dramatic than the decline seen within the White <br /> River. This contrasts with the fact that mercury concentration measurements have been lower in <br /> Colorado pikeminnow taken from the Yampa River than from the White River. <br /> While some Colorado pikeminnow individuals are likely to be experiencing low-level harmful <br /> effects from mercury in the system,we do not believe that the additional amount of mercury <br /> from the project will be enough to significantly or measurably reduce population numbers, <br /> reproduction, or constrain Colorado pikeminnow distribution. <br /> 4.3.3.2 Razorback sucker <br /> The effects to the razorback sucker from project-generated mercury are similar to those <br /> described for the Colorado pikeminnow above, although likely to be less severe in the action <br /> area. The razorback sucker is not a piscivorous fish and would not bioaccumulate mercury as <br /> rapidly. Additionally,the razorback sucker does not occur as far upstream in the Yampa and <br /> White Rivers as the Colorado pikeminnow; thus, it does not occur as close to the point-sources <br /> for mercury resulting from the project. As with the Colorado pikeminnow, we believe nonnative <br /> species are the primary limiting factor for razorback sucker numbers, successful recruitment, and <br /> their distribution within the action area. While the evidence indicates that some razorback <br /> sucker individuals are likely being adversely affected by mercury in the system,we do not see <br /> evidence indicating that the negative effects from mercury rise to the level of reducing <br /> population numbers, are limiting reproduction, or are constraining razorback sucker distribution. <br /> 4.3.3.3 Humpback chub <br /> The effects to the humpback chub in the action area from project-generated mercury are similar <br /> to those described for the Colorado pikeminnow above, although perhaps less severe. The <br /> humpback chub is not a top predator and may not bioaccumulate mercury as rapidly. <br /> Additionally, the humpback chub does not occur as far upstream in the Yampa River as the <br /> Colorado pikeminnow, and is not known to occupy the White River in any significant way; thus, <br /> it does not occur as close to the point-sources for mercury resulting from the project. As with the <br /> Colorado pikeminnow,we believe nonnative species are the primary limiting factor for <br /> humpback chub numbers, successful recruitment, and their distribution within the action area. <br /> While the evidence indicates that some humpback chub individuals are likely being adversely <br /> affected by mercury in the system,we do not see evidence indicating that the negative effects <br /> from mercury rise to the level of reducing population numbers, are limiting reproduction, or are <br /> constraining humpback chub distribution. <br /> 4.3.3.4 Bonytail <br /> The effects to the bonytail in the action area from project-generated mercury are similar to those <br /> described for the Colorado pikeminnow above, although perhaps less severe. The bonytail is not <br /> a top predator and may not bioaccumulate mercury as rapidly. Additionally,the bonytail does <br /> not occur as far upstream in the Yampa River as the Colorado pikeminnow, and has only <br /> recently been stocked into the lower White River; thus, it does not occur as close to the <br /> 53 <br />