YCT Multi-state Assessment February 10, 2003 



Conservation Populations 



A total of 195 populations of YCT (both spotting forms combined) occupying about 6,346 miles 

 of habitat (over 84% of currently occupied habitats; 36% of historical range) were identified as 

 conservation populations (Figure 6; Appendix F). These designated conservation populations 

 were spread throughout the historical range, occurring in 35 of the 41 HUC's historically 

 occupied by YCT. These conservation populations were obviously more densely concentrated 

 within the core of the historical range than near the fHnges (Figure 6). Individual conservation 

 populations occupied from 0.3 to over 1,500 miles of habitat (median = approximately 10 miles: 

 Figure 7). The distribution of lengths of habitat occupied by conservation populations was 

 skewed with most of the populations (126) occupying 10 miles or less. Most conservation 

 populations were isolets (143) that occupied a total of 831 miles of habitat (Table 12). A total of 

 52 meta-populations occupying 5,515 miles of habitat were identified. 



Of the 195 designated conservation populations, 39 (20%) were considered as "core" 

 conservation populations having been tested and found to be genetically unaltered (Table 12). 

 These core conservation populations occurred as 37 "isolates" and 2 meta-populations that 

 occupied approximately 236 miles of habitat (11% of current habitat and 5% of historical 

 habitat). There were an additional 10 conservation populations that were comprised of stream 

 segments tested as unaltered and segments that were untested but felt to be potentially unaltered. 

 There were also 84 populations (71 isolates and 13 meta-populations) made up solely of 

 potentially unaltered stream segments. In combination, conservation populations that were 

 tested unaltered with those believed to be unaltered would bring the total of "core" conservation 

 populations to a total of 133. A total of 61 conservation populations included stream segments 

 suspected of being altered and segments known to be introgressed based on genetic testing 



The amount of habitat occupied by "core" populations known to be genetically unaltered was 

 estimated to at 235 miles (about 3% of currently occupied habitat; slightly more than 1% of the 

 historical habitat). There were approximately 685 stream miles (9% of current; 4% of historic) 

 associated with conservation populations believed to be potentially unaltered and another 949 

 miles (13% of current; 5.4% of historic) composed of a mixture of tested unaltered and 

 potentially unaltered. In combination, there were 133 potential "core" populations (1,870 miles; 

 24.8%) of current and 10.7%) of historic) of YCT with stream segments existing as tested 

 unaltered, or a combination of tested and potentially unaltered or only potentially unaltered. 

 Conservation populations composed of suspected altered stream segments and those composed 

 of mixture of tested altered and varying combinations of altered and other genetic makeup 

 comprised, 580 and 3,896 miles, respectively. 



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