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Ira W. Hatch, District Ranger <br />"Reasons for decline of most native fishes in the Colorado River <br />Basin have been attributed to habitat loss due to construction of <br />mainstream dams and subsequent interruption or alteration of natural <br />flow and physio- chemical regimes, inundation of river reaches by <br />reservoirs, channelization, water quality degradation, introduction <br />of nonnative fish species and resulting competitive interactions or <br />predation, and other man - induced disturbances (Miller 1961, Joseph <br />et al. 1977, Behnke and Benson 1983, Carlson and Muth 1989, Tyus and <br />Karp 1989). These factors are almost certainly not mutually <br />exclusive, therefore it is often difficult to determine exact cause <br />and effect relationships." <br />The virtual absence of any recruitment suggests a combination of biological, <br />physical, and /or chemical factors that may be affecting the survival and <br />recruitment of early life stages of razorback suckers. Within the Upper <br />Basin, recovery efforts endorsed by the Recovery Implementation Program <br />include the capture and removal of razorback suckers from all known locations <br />for genetic analyses and development of discrete brood stocks if necessary. <br />These measures have been undertaken to develop refugia populations of the <br />razorback sucker from the same genetic parentage as their wild counterparts <br />such that, if these fish are genetically unique by subbasin or individual <br />population, then separate stocks will be available for future augmentation. <br />Such augmentation may be a necessary step to prevent the extinction of <br />razorback suckers in the Upper Basin. <br />Critical Habitat <br />Critical habitat has been proposed within the 100 -year floodplain of the <br />razorback sucker's historical range in the following sections of the Upper <br />Basin, which are pertinent to this project (58 F.R. 6578): <br />Utah, Uintah, Carbon, Grand, Emery, Wayne, and San Juan Counties. The <br />Green River and its 100 -year floodplain from Sand Wash at river mile 96 <br />at T. 11 S., R. 18 E., section 20 (6th Principal Meridian) to the <br />confluence with the Colorado River in T. 30 S., R. 19 E., section 7 <br />(6th Principal Meridian). <br />Utah, Grand, San Juan, Wayne, and Garfield Counties. The Colorado River <br />and its 100 -year floodplain from Westwater Canyon (river mile 125) in <br />T. 20 S., R. 25 E., section 12 (Salt Lake Meridian) to full pool <br />elevation, upstream of North Wash, and including the Dirty Devil arm of <br />Lake Powell in T. 33 S., R. 14 E., section 29 (Salt Lake Meridian). <br />Biology <br />Specific information on biological and physical habitat requirements of the <br />razorback sucker is very limited. Until very recently, fisheries research <br />investigations throughout the Upper Basin have focused on the other three <br />listed Colorado River fishes, and data collected on the razorback sucker was <br />largely coincident to those studies. Localized extirpation of razorback <br />R1 <br />