Table 1. Genetic classes used for assessing genetic status of westslope cutthroat trout in 2002. 



Code Description Report name 



A Genetically unaltered (<1% introgression) -tested via Tested; Unaltered 



electrophoresis or DNA 



B Introgressed < 10% - tested via electrophoresis or DNA Tested; <= 10% 



introgressed 



C Introgressed >10% and < 25% - tested via electrophoresis or Tested; <=25% to > 10% 



DNA introgressed 



D Introgressed >25% - tested via electrophoresis or DNA Tested; > 25% introgressed 



H Suspected unaltered with no record of stocking or Suspected Unaltered 



contaminating species present 



J Potentially hybridized with records of contaminating species Potentially Altered 



being stocked or occurring in stream 

 N Hybridized and Pure populations co-exist in stream (use only Mixed Stock; Altered and 

 if reproductive isolation is suspected and testing completed) Unaltered 



Genetic tests can detect introgression between WCT and potentialy introgressing species or 

 subspecies by fmding alleles unique ("diagnostic alleles") to that potentially introgressing 

 species or subspecies within WCT populations. The number, and thus the proportion, of 

 potentially introgressing species or subspecies "diagnostic" alleles within WCT populations, is 

 used to estimate the level of introgression. One consequence of this approach is that proving a 

 stock of WCT to be genetically pure is essentially impossible: all individuals in a population 

 would have to be tested. Therefore, sample size must be considered when evaluating the 

 reliability of any genetic test. Generally, sample sizes should be large enough to determine, with 

 a pre-determined level of statistical reliability (95% has often been used), that a 1% or less level 

 of introgression would be detected. Both the number offish sampled and the number of alleles 

 that are "diagnostic" between species or subspecies determine the sample size needed for a pre- 

 determined level of statistical reliability. Thus, when genetic testing finds no evidence of 

 introgression, sample size is very important for assessing how valid the result may be. For this 

 assessment we reported results of all genetic testing, regardless of sample size, and then 

 displayed and summarized sample sizes for all genetic testing. 



Different genetics laboratories, and sometimes even the same lab, may report genetic results 

 differently; consequently, it can be difficult to compare genetic results across broad geographic 

 areas. Especially when brief summaries of these data are stored in standardized fish resource 

 databases. An example of where this type of problem may occur is that of a mixed stock 

 population, where some individuals within the population may be genetically unaltered WCT 

 and other individuals may be genetically unaltered rainbow trout (RBT). Unless either the local 

 fisheries professional or the database indicated that non-random mating was occurring (code N; 

 Table 1), we assumed genetic results were a function of random mating. If random matings were 

 incorrectly assumed to be operating for the above hypothetical mixed stock population, genetic 

 sample results would indicate introgression at levels in proportion to the proportion of RBT to 

 WCT for this hypothetical population. Where there was evidence of non-random mating, some 



Page - 6 



