Sample Details: 



Bitterroot River: Four individuals in this sample exiiibit PINE fragments diagnostic of 

 only westslope cutthroat trout. One individual displays PINE fragments characteristic of 

 an Fl hybrid of westslope cutthroat trout and rainbow trout. Five individuals were post- 

 Fl hybrids of westslope cutthroat trout and rainbow trout. As a main stem sample, this 

 does not represent a single population, and further analysis is not possible. 



Rattlesnake Creek: All 23 successfully amplified individuals in this population 

 displayed PINE fragments diagnostic of westslope cutthroat trout and rainbow trout. 

 Assuming random mating proportions, the genetic contributions of westslope cutthroat 

 and rainbow trout are 60.8% and 39.2%, respectively. With a sample size of 23, we have 

 a 94% chance of detecting as little as 1% hybridization between westslope cutthroat and 

 rainbow trout. 



This population was also tested for introgression with Yellowstone cutthroat trout. No 

 evidence of Yellowstone cutthroat trout introgression was found. With a sample size of 

 23, we have an 84% chance of detecting as little as 1% hybridization. 



Fish Creek: All 25 successfully amplified individuals in this population displayed PINE 

 fragments diagnostic of westslope cutthroat trout. However, three fish also exhibited 

 characteristic rainbow trout markers. Assuming random mating proportions, the genetic 

 contributions of westslope cutthroat and rainbow trout are 98% and 2%, respectively. 

 With a sample size of 25 individuals, we have a 95% chance of detecting as little as 1% 

 hybridization between westslope cutthroat trout and rainbow trout. 



This population was also tested for introgression with Yellowstone cutthroat trout. No 

 evidence of Yellowstone cutthroat trout introgression was found. With a sample size of 

 25, we have an 87%) chance of detecting as little as l%o hybridization. Without a larger 

 sample size, we camiot exclude the possibility that this population may also be slightly 

 hybridized with Yellowstone cutthroat trout. 



Cottonwood Creek: All 24 successfully amplified individuals in this population 

 displayed only FINE fragments diagnostic of westslope cutthroat trout. With a sample 

 size of 24 individuals, we have a 94% chance of detecting as little as 1% hybridization 

 with rainbow trout and an 85% chance of detecting as little as 1% hybridization with 

 Yellowstone cuttliroat trout. This sample appears to have come from a pure westslope 

 population, but we cannot reasonably exclude that it might be hybridized with either 

 rainbow or Yellowstone cutthroat trout. With a larger sample size, a more accurate 

 analysis is possible. 



