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<br />~ .. . <br /> <br />24 Chapter 2.0 Description of Alternatives <br /> <br />2.3 POTENTIAL MEANS TO ALLEVIATE ADVERSE EFFECTS OR <br />REDUCE INCIDENTAL TAKE <br /> <br />Kanab Ambersnail. - The projected loss of habitat at Vaseys Paradise from the <br />proposed action will not exceed the amount lost during the 1996 BHBF, and it will not <br />exceed the incidental take estimated by the Service (2000), however, the GCDAMP has <br />advocated that acceptable means be determined to meet incidental take requirements <br />before the experimental high releases are conducted (Winfree et al. 2001). In 1996, <br />incidental take was diminished by relocation of snails to higher elevations at Vaseys <br />Paradise. This approach is not advocated by the GCDAMP for long-term management <br />in conjunction with controlled high releases (Winfree et al. 2001). Two other means of <br />reducing incidental take are establishment of a refugium or experimental population <br />and augmentation of the upper Elves Chasm population. Establishment of an <br />experimental population was considered by the GCDAMP and advocated "when they <br />are needed for research that is in the species best interests" (Winfree et al. 2001). <br />Augmentation of existing translocated populations was not ruled out by the GCDAMP <br />if that action is "to sustain and maintain existing populations at the translocation sites <br />and meet the original objectives of the current Recovery Plan and Biological Opinion" <br />(Winfree et al. 2001). Therefore, both of these actions will be evaluated for reducing the <br />incidental take from this action. <br /> <br />An expert panel convened in December 1999 concluded that controlled floods from <br />Glen Canyon Dam produce little danger of extirpation for the Vaseys Paradise KAS <br />population (Noss et al. 1999). The panel advocated that "initial take of 40% would <br />almost certainly not threaten the persistence of the snail population." Their conclusion <br />was based largely on the premise that this population has been present at Vaseys <br />Paradise for millennia and has withstood the vagaries of floods of much greater <br />magnitude and frequency in the predam era. An ad hoc committee to the Technical <br />Work Group of the GCDAMP assessed the expert panel's findings and concluded that <br />they did not have sufficient historical information about Vaseys Paradise or other KAS <br />populations to concur with the expert panel on the level of take that would endanger the <br />Vaseys Paradise population (Winfree et al. 2001). The ad hoc committee did advocate <br />that "the potential for ecological benefits warrants continued planning for high flows <br />and other experimental flows." <br /> <br />Humpback chub.-Robinson et al. (1996) investigated survival of young HBC in the <br />perennial reach of the lower Little Colorado River above the fishes' present distribution. <br />By isolating them in experimental cages, they determined HBC could survive in that <br />reach. They also concluded that food and habitat in that reach were suitable, but that the <br />fish likely were precluded from entrance to the reach by travertine barrier falls. Among <br />their recommendations were that consideration be given to breaching the falls to allow <br />passage of humpback chub into the unoccupied reach. The proposed action provides an <br />opportunity to conduct an experiment at establishing a population of humpback chub in <br />the unoccupied reach by collecting young-of-year from the reach below the falls and <br />stocking them above the falls. This action would require the permission and cooperation <br />