WCT Multi-state Assessment February 10, 2003 



additional waters are being managed with restrictive fishing regulations, and there has been 

 considerable effort directed at maintaining and improving habitat conditions. Furthennore. 

 drought conditions in the mid to late 1980s may have temporarily depressed fish populations. 

 New information, responses of some populations to protective measures, and assessments made 

 during drought conditions without the benefit of long term trend data may all contribute to 

 discrepancies between this analysis and that of Rieman and Apperson (1989). 



Conversely, Lee et al. (1997) and Thurow et al. (1997) estimated that WCT occupied 85% of 

 their historical range in the upper and middle Columbia River basin by subwatershed (6 ^ code 

 level HUC). Their findings were slightly higher than ours, but were more consistent with our 

 results because they considered any occurrence of WCT within a subwatershed as occupancy and 

 we delineated the actual lengths of occupied and vacant habitats. 



Liknes (1984) and Liknes and Graham (1988) estimated that WCT occurred in 27% (4.280 

 miles) of their historical range in Montana and that genetically unaltered WCT occupied only 

 2.5% (390 miles) of the historical range. Van Eimeren (1996) estimated that WCT occupied 

 about 19% of an historical range that he estimated was 57,000 miles, or occupancy of about 

 10.800 miles in Montana. For Montana, we estimated that WCT currently occupied almost 

 13.000 miles (39% of what we considered historical range) and genetically unaltered WCT 

 occupied almost 3.000 miles (9% of historical range). While the miles of habitats currently 

 occupied by WCT differed among these three assessments, we believe the primary reasons for 

 these differences are the discovery of both more streams that support WCT, due to increased 

 survey efforts, and increased genetic sampling over time. 



Other assessments of WCT status and distribution (Liknes and Graham 1988: Mamell 1988: 

 Rieman and Apperson 1989: Thurow et al. 1997) suggested that wilderness and roadless areas 

 provide important strongholds for WCT. While this assessment supports these previous findings, 

 the relationship between abundance of WCT and presence of wilderness or roadless areas is 

 confounded by the lack of independence between abundance classifications and habitat quality, 

 particularly for those stream segments where abundance class was based on professional 

 judgment (Table 14). 



Designated Conservation Populations 



There are two types of conservation strategies represented in how the states designated WCT 

 "conservation populations". One strategy emphasizes conserving genetic integrity by isolating 

 WCT populations that have no evidence of genetic introgression to prevent introgression and 

 competition by nonnative fish. The other strategy emphasizes maintaining connectivity among 

 WCT populations by protecting relatively large areas of continuous habitat that will allow WCT 

 to express all life-history traits, especially migratory life-histories. As we showed in the results, 

 the types of risks inherent in these two different conservation strategies are dramatically 

 different. 



For those WCT populations where genetic integrity is emphasized, risks due to isolation, small 

 population size, and temporal variability are high, while other types of risk are relatively low. 

 The assumption made in rating these population risks as high is that WCT populations need to 

 occupy relatively large habitats that allow for connection among many subpopulations. Some 



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