WCT Multi-state Assessment February 1 0, 2003 



Genetic Risks 



Genetic risk was defined by the risk of future introgression of WCT in a conservation population. 

 Distance from potential sources of anthropogenic introgression and the presence of documented 

 barriers between those sources and the conservation population were the two primary 

 components that were assessed to determine genetic risk (Table 4). In addition, where there was 

 documented e\'idence indicating that potentially introgressing species or subspecies were 

 reproductively isolated from WCT. due to either temporal or spatial isolation during spawning, 

 the genetic risk rating for that conservation population was reduced. The potential for natural 

 introgression with either native redband or steelhead trout (O. mykiss) was not considered a 

 genetic risk for those watersheds where these species co-evolved w ith WCT. Normative 

 salmonids that could potentially hybridize with WCT, had been stocked, either legally or 

 illegally, and were now reproducing naturally in the wild, were considered as posing a genetic 

 risk to WCT. 



Table 4. Ranks and descriptions used for assessing genetic risks to designated conservation 

 populations of westslope cutthroat trout in 2002. Hybridizing species includes any 

 introduced species or subspecies, but exclude native species (inland redband and 

 steelhead trout), that could potentially hybridize with westslope cutthroat trout. 



Rank Activity 



1 Hybridizing species CANNOT FNTERACT with existing WCT population. Barrier 

 provides complete blockage to upstream fish movement. 



2 Hybridizing species are in same stream and/or drainage FURTHER THAN 10 KM from 

 WCT population, but not in same stream segment as WCT, or may be WITHIN 10 KM 

 WHERE BARRIER EXISTS, BUT MAY BE AT RISK OF FAILURE. 



3 Hybridizing species are in same stream and/or drainage WITHIN 10 KM of WCT 

 population and NO BARRIER EXISTS; however, hybridizing species not yet found in 

 same stream segment as WCT population. 



4 Hybridizing species are SYMPATRIC with WCT population in same stream segment. 



Disease Risks 



A disease risk assessment was made for each conservation population using a ranking of 1 to 5 to 

 indicate low to progressively higher levels of risk associated with the potential influence of 

 significant diseases (Table 5). Population isolation and security were important considerations 

 but were not viewed as absolutes. Diseases of concern were those that could cause severe and 

 significant impacts to population health and included, but were not limited to, whirling disease, 

 furunculosis. and infectious pancreatic necrosis virus. Disease risk assessments were either 

 completed or reviewed by fish health professionals from the respective state's fish and wildlife 

 agencies. The level of risk was not viewed as an absolute but rather as an indicator of potential 

 risk. 



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