YCT Multi-state Assessment February 1 0, 2003 



Of the 195 conservation populations, 138 (71%) were comprised of only the large-spotted form, 

 39 (20%) were comprised of only the fine-spotted form and 18 (9%) represented a mixture of 

 both spotting patterns (Figure 1 1; Table 16). Large-spotted YCT conservation populations were 

 identified as being broadly distributed throughout the range. Large-spotted YCT existing 

 without the presence of the fine-spotted form occurred in 3,888 miles of stream (61.3% of habitat 

 occupied by conservation populations). The fine-spotted form exisfing without the presence of 

 the large-spotted form occurred in 217 miles of stream (3.4%). Conservafion populations having 

 representatives of both spotting patterns occurred in 2,241 miles of stream (35.3%). 

 Conservafion populations with only fine-spotted YCT were primarily located within headwaters 

 of the Snake River. A few fine-spotted YCT conservation populations were identified outside of 

 the Snake River basin (Figure 11). It should be noted that the fine-spotted form had been widely 

 used within the recreational fishery management program for Wyoming and because of this they 

 have been introduced into many watersheds outside the initial area they occupied 



Of the 138 large-spotted YCT conservation populations, 38 had sufficient genetic testing to 

 determine that they were unaltered and could be considered as "core" populations. Another 8 

 conservation populations were comprised of stream segments containing both tested pure and 

 segments viewed a potentially unaltered. Forty (40) conservation populations were treated as 

 potentially unaltered and 25 were suspected of being genetically altered. Another 27 populations 

 were either tested and found to be genetically altered or they existed as a mixture of altered and 

 unaltered YCT. Seventy two percent of the large-spotted YCT populations were isolates and 

 28% were meta-populations. 



For the conservafion populations (39) having only the fine-spotted form, most (36) were 

 identified as being potentially unaltered and three were suspected of being altered. Thirty four of 

 these fine-spotted YCT conservation populations were isolates and five were meta-populations. 

 A total of 1 8 conservation populations had both fine and large-spotted YCT present. These 

 conservation populations were nearly equally split between isolates (56%) and meta-populations 

 (44%). There was only one "core" conservation population identified in this mixed stock group. 

 As more genetic testing is completed we anficipate that many of the populations having 

 potentially unaltered stream segments will be found to be unaltered. Genetic alteration 

 (introgression) alluded to in this assessment is between YCT, and rainbow trout or other formally 

 recognized cutthroat subspecies (AFS 1991) with no differenfiation between the spotting 

 patterns. 



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