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So, it appears that the Snake Valley population, as well as other sub-basin specific populations, could have evolved through events possibly during relatively short periods of desiccation, when trout were isolated in Snake Valley, and in other areas ofthe basin. As lake levels rose again, the trout may have maintained reproductive isolation in their parent stream. Such reproductive isolation would have allow_ed sufficient time for considerable genetic divergence. The presence of this unique race should be concern for protection of remaining relic populations throughout the basin. It is recognized that BCT are a diverse group within the cutthroat trout subspecies. Scientists recommend the various existing populations should be considered unique entities and mixing of the groups should be avoided (Behnke and Zarn 1976, Shiozawa, Evans and Williams 1993). While some stream populations survive, the BCT evolved primarily in a lake (lacustrine) environment. Upon desiccation of Lake Bonneville, trout were primarily restricted to perennial tributaries, and connected watersheds and sub-basins; only Bear Lake, Utah Lake, and Panguitch Lake retained lacustrine populations. These historic lake populations have been extirpated except in Bear Lake. Remaining BCT populations in the Bonneville Basin are a unique evolutionary and biological heritage of the Great Basin. However, during the last 150 years the Bonneville cutthroat trout metapopulations have been significantly reduced through anthropogenic activities. This loss of connectivity to sub. basins, non-native introductions, habitat fragmentation, and decreases in BCT throughout the Basin continue to threaten its recovery and may even preclude its Mure survival. In the most recent comprehensive review of the taxonomy and distribution of cutthroat trout, Behnke (1992) separates BCT into three slightly differentiated groups associated with: (1) the Bonneville Basin proper (including the Ogden, Provo, Weber, and Sevier River drainages); (2) the Snake Valley of Utah; and (3) the Bear River drainage. Research by Shiozawa et al. (1993) also categorized the Bonneville cutthroat trout into three main subgroups: (1) the Bear River form; (2) the Southern Bonneville form (actually described from the Virgin River drainage); and (3) the main Bonneville Basin form. However, for the purposes of this habitat conservation assessment (HCA) , I will differentiate the cutthroat trout groups within the Bonneville Basin into four hydro-geographic areas: (1) Bear River Bonneville cutthroat trout (BRB) , including those population within the Bear River basin of Utah, Idaho, and Wyoming, from its headwaters to entry into the Great Salt Lake; (2) Northern Bonneville cutthroat trout (NB), which includes the waters of the Ogden, Weber. Jordan, and Spanish Fork Rivers, and the Utah Lake sub-basins; (3) Southern Bonneville cutthroat trout (SB), which includes the Sevier River, Sevier Lake, and Escalante Desert sub-basins, as well as the Upper Virgin River sub-basin in the Colorado River Basin, where several. transplanted populations exist; and (4) Western Bonneville cutthroat trout (WB), which includes the Utah-Nevada portion of the Great Salt Lake Desert, from the Raft River Range on the north to the Snake Valley area on the south, also including a .closed sub-basin" in adjacent Nevada, where several transplanted populations occur (Figures 2 and 3). ASSESSMENT METHODS The assessment conducted for BCT populations was outlined in the HCA Introduction section. State and federal fisheries managers within the Bonneville Basin (Utah, Nevada, Wyoming, and Idaho) were contacted and provided the HCA questionnaire for completion. In addition, others with experience and expertise in BCT occurrence and distribution were contacted, including individuals from universi- ties, other state and federal agencies, and conservation groups. 37