extremely problematic. This will require a large number of markers because the hybrid 

 individuals collected were definitely later than first generation hybrids. Thus, with a 

 relatively small number of markers many hybrids will be indisfinguishable from 

 westslope cutthroat trout. From a management perspective, therefore, based on this 

 sample the populafion should simply be considered to have been hybridized with rainbow 

 trout. 



Game Creek (#2261) 



This tributary to Union Creek sampled June 22, 2002 was initially reported as appearing 

 to have come from a non-hybridized westslope cutthroat trout population. I strongly 

 disagree with this conclusion. 



Again, there appeared to be some problem with obtaining DNA fi"om the samples and/or 

 in the polymerase chain reaction (PCR) used to copy the DNA as data are really available 

 from only four of the six diagnostic loci that we normally analyze that usually distinguish 

 rainbow trout from westslope cutthroat trout. The sample originally was erroneously 

 reported as containing two individuals with a fragment characteristic of rainbow trout at 

 only one, and the same, diagnostic locus. The other 23 fish in the sample possessed 

 PINE fragments characteristic of only westslope cutthroat trout. In this situation, there 

 are two possible interpretations of the data. The populafion could be slightly hybridized 

 with rainbow trout or the variation detected could simply be westslope cutthroat trout 

 genetic variation that is electrophoretically indistinguishable from that usually 

 characterisfic of rainbow trout. Because of the uncertainty about whether or not the 

 sample came from a hybridized population, conservatively it was suggested it be 

 considered to be non-hybridized westslope cutthroat trout. 



Rechecking the data revealed that the two fish in the sample reported as possessing a 

 PINE fi-agment characterisfic of rainbow trout at one of the four diagnostic loci analyzed 

 actually possessed PINE fragments characteristic of rainbow trout at two diagnosfic loci. 

 These two fish, therefore, were almost undoubtedly of hybrid origin. The PINE 

 fragments characteristic of rainbow trout, however, were not randomly distributed 

 P<0.001) among the fish in the sample suggesting that at the fime of sampling the 

 population most likely contained a mixture of non-hybridized westslope cutthroat trout 

 and fish of hybrid origin. For the same reasons as in the Union Creek populafion, 

 conclusively determining which individuals are non-hybridized in Game Creek will be 

 extremely problematic. From a management perspective, therefore, based on this sample 

 the populafion should simply be considered to have been hybridized with rainbow trout. 



Fish Creek (#2277) 



This sample collected September 10, 2001 was initially reported as having come fi-om a 

 hybrid swarm with about a 98% westslope cutthroat and a 2% rainbow trout genetic 

 contribution. I do not completely agree with this interpretation, but again this 

 disagreement probably will not change how the populafion is viewed genetically from a 

 management perspective. 



