WSP00287 - Laserfiche WebLink

Home Browse Search

. . (ca. 160C), which keep the microenvironment warm enough to prevent freezing during moderately cold winter months. Also, warm winters, such as 1995-1996, do not freeze watercress back, while cold winters (e.g. 1990) freeze and kill the plants. Warm spring flow and warm winters decouple the watercress life cycle from climate, and limit predictability of habitat conditions. Demographic analyses based on size class distribution indicate that KAS is essentially an annual species, with much of the population maturing and reproducing in mid- summer (July and August), and most snails over-wintering as small size classes (Kanab Ambersnaillnteragency Work Group 1997b). Loose, gelatinous egg masses were observed on the undersides of moist to wet live stems, on the roots of water-cress, and on dead or decadent stems of crimson monkey-flower in mid-summer of all years of study. No data on egg development or emergence success are presently available. In warm winters, such as that of 1995-96, KAS may emerge from dormancy early, and produce a double generation within one year (Kanab Ambersnaillnteragency Work Group 1997a). KAS at Vaseys Paradise are parasitized by the trematode flatworm, Leucochloridium cyanocittae, with 1.0% to 9,5% of the mature snails expressing sporocysts in mid- summer from 1995 through 1997 (Stevens et al. 1997b, Kanab Ambersnaillnteragency Work Group 1997 a,b), Potential vertebrate predators of KAS at Vaseys Paradise include deer mice (Peromyscus crinitus and P. maniculatus), as well as rainbow trout (Oncorhynchus mykiss) in the stream mouth), resident common raven (Corvus corax) and canyon wren (Catherpes mexicanus), summer breeding Says and black phoebe (Sayornis ~ and S, nigricans). and winter resident American dipper (Cinclus mexicanus), Impacts of BHBF In its 21 December 1994, Final Biological Opinion (B.O.) the Service evaluated impacts to KAS from the operation of Glen Canyon Dam according to operating and other criteria of the Preferred Alternative in the GCDEIS, The Service determined implementation of the Preferred Alternative would not jeopardize the continued existence of the KAS. The 1994 B.O, also supported the concept of BHBFs as part of the preferred alternative, and indicated that incidental take of KAS will assume to be exceeded if more than 10% of the occupied habitat in Grand Canyon will be inundated by high flows or a controlled flood. The 1996 B.O. recognized the importance of BHBFs for ecosystem management, but included as Reasonable and Prudent Measures mitigation of impacts by moving snails in the flood zone to higher locations immediately prior to the BHBF, Stevens et al. (1997b, Kanab Ambersnaillnteragency Work Group 1997a) predicted the 1996 BHBF would result in a KAS habitat loss of 16.1 %, and KAS population losses of 11.4% to 16.4%, without mitigation through translocation, A total of 1,275 KAS were transferred upslope of the 45,000 cfs stage in the week preceding the 1996 BHBF, reducing the 1998 GCD Beach/Habitat Building Flow 9 Biological Assessment