WCT Multi-state Assessment February 10, 2003 



from Washington. This stocking likely explains why WCT are now found in Lake Creek, which 

 drains Olive Lake. 



Current Distribution 



WCT currently occupy about 33.500 miles (59%) of the nearly 56.500 miles of historically 

 occupied habitats. However, the genetic status of WCT across all this area has not been 

 detennined by genetic testing. WCT currently occupy over 1 8.000 miles in Idaho (95% of 

 historical), almost 13.000 miles in Montana (39% of historical), about 250 miles in Oregon (21% 

 of historical), and almost 2.000 miles in Washington (66% of historical). 



•* Genetic Status 



Most sampling for genetic testing was probably not done randomly. Consequently, the available 

 genetics infonnation probably does not constitute a simple random sample taken from the entire 

 WCT population. Instead, there probably was a tendency to sample fish from populations that 

 included fish that appeared to be phenotypic WCT. Genetic sampling has been conducted in 

 over 6.100 miles of occupied habitats (18% of occupied habitats). No evidence of introgression 

 was found from samples covering about 3.400 miles (56% of tested area. 10% of occupied 

 habitats, and 6% of historical habitats; Table 9: Figures 2 and 3: Appendix F). WCT that made 

 up part of a mixed stock population and were not introgressed occupied another 1.037 miles for a 

 total of non-introgressed WCT occupying over 13% of currently occupied habitats. WCT that 

 inhabited over 9.100 miles (27% of occupied habitats and 16% of historical habitats) are 

 suspected of being genetically unaltered, based on the absence of introduced hybridizing species. 

 WCT in about 17.300 miles (52% of occupied habitats and 31% of historical habitats) could 

 possibly be hybridized due to the presence, or past stocking, of potentially hybridizing normative 

 species or subspecies. In addition to those habitats within historical range that were occupied by 

 WCT, we recorded information on WCT that currently occupy about 350 miles of habitat outside 

 their historical range, but many stream segments that support WCT outside their historical range 

 were not included (Table 9). 



To better evaluate the quality of genetic sampling, we looked at the sample sizes of genetic 

 sampling events related to whether more or less than a 1% level of introgression was found 

 (Figure 4). The number offish sampled represents each sampling event and. in some cases, 

 more than one sampling event were probably pooled, but we had no way of assessing pooled 

 samples. Of those samples that indicated a level of introgression of 1% or less. 30% had 25 fish 

 or more and over 39% had 20 fish or more in the sample. Most genetic testing techniques allow 

 for a 95% confidence at detecting a 1% level of introgression with a 25 fish sample. 



Page- 17 



