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<br />. <br /> <br />. <br /> <br />during a 45,000 cfs BHBF, which exceeds the level of habitat take allowed in the 1994 <br />Biological Opinion by 4%, However, a total of 27.71 m2 of the habitat lying below the <br />45,000 cfs stage in the October 1997 survey consisted of mixed vegetation patches <br />dominated by horsetail (Equisetum spp.), reed (Phragmites australis) and other <br />species. These patches are little used by KAS, and are extremely resistant to scour, <br />having persisted through the 1996 BHBF and the high flows of 1997. If this portion of <br />the habitat is excluded from the calculation of primary KAS habitat, only 73,51 m2 <br />(10.2%) of the estimated total primary habitat will be at risk during 1998 BHBF(s). For <br />reference, the 1996 BHBF removed 119.4 m2 of habitat and would have eliminated an <br />estimated 2,126 KAS had not 1,275 KAS been moved to higher stage elevations. <br /> <br />If the above habitat assumptions are accurate, and if KAS densities are equivalent <br />across stage elevation (Kanab Ambersnaillnteragency Work Group 1997b), and if <br />winter mortality is negligible or proportional among stage zones, as many as an <br />estimated 2,187 KAS (8.4% of the estimated total population of 26, 129 KAS) may be <br />lost during 1998 BHBF(s) at 45,000 cfs, <br /> <br />Conclusions <br /> <br />The introduction of non-native watercress and the construction of Glen Canyon Dam <br />has increased primary KAS habitat area at Vaseys Paradise by more than 40%, and <br />has undoubtedly substantially increased the snail population, In the pre-dam era, the <br />KAS population at Vaseys Paradise survived and recovered from innumerable flows <br />equal to or higher than 45,000 cfs BHBFs. After the initial >2-yr period of development <br />of the new, post-dam vegetation, the KAS population survived seven flows of ?,45,OOO <br />cfs during the post-dam era (Le., 1965, 1980, 1983-1986, and 1996). <br /> <br />Although the cumulative impact of incremental take from repeated high flows is a <br />concern, the >2 yr recovery period for KAS habitat at Vaseys Paradise documented by <br />the Kanab Ambersnaillnteragency Work Group (1997b) indicates that the KAS <br />population has existed in a state of recovery from flows of ?,45,OOO cfs for at least 16 of <br />the past 34 years (?,47% of post-dam time), Therefore, the KAS habitat lying in the <br />BHBF flood zone has often re-developed following large flows, and flows of 45,000 cfs <br />are unlikely to affect the long-term integrity of the KAS population. <br /> <br />Reclamation concludes that: <br /> <br />. the Vaseys Paradise KAS population appears to be relatively large and self- <br />sustaining; <br /> <br />. more than 40% of the present primary KAS habitat at Vaseys Paradise lies <br />below the pre-dam 1 O-year flood stage of 125,000 cfs and is new, post-dam <br />habitat; <br /> <br />. the KAS population has survived numerous larger floods both before and after <br /> <br />1998 GCD Beach/Habitat Building Flow 11 <br /> <br />Biological Assessment <br />