17 



Trout abundance was higher overall in control stations than in urban stations 

 with respect to all four expressions of abundance that were calculated (Table 2). | 

 Trout abundances expressed per unit of stream length showed much greater statistical I 

 significance of urban-vs-control differences than did per-unit-area expressions. 

 In terms of kilograms per stream kilometer, control areas had lk% more trout than 

 urban areas did, a difference significant at the 97-5% confidence level. In 

 Bozeman Creek, the control sections averaged 83% more kg of trout per km, a 

 difference significant at the 99% level. The urban-vs-control differences 

 in terms of number of over-20-cm (over-8-inch ) trout per kilometer were significant 

 at the 85% level overall and at the 98% level for Bozeman Creek, which had the 

 majority of stations. 



It can be concluded that the results are consistent with the hypotheses 

 of this study: (1) that key habitat variables are less favorable for trout in 

 altered (urban) than in less altered stream sections, and (2) that trout are 

 less abundant in the more altered sections. The following sections of this 

 report further support these conclusions and provide some information toward 

 identifying possible causative processes. 

 Application of the Wyoming HQI 



Application of the Wyoming Habitat Quality Index Model II (Binns 1979) to 

 the data from all 30 study stations yielded poor correlation (r = 0.228) between 

 predicted and actual standing crops of trout expressed as kg/ha (Table -3, Figure 

 3), however it appears that if data from study sections (combinations of contiguous 

 stations) were plotted instead of stations, variability would be reduced and the 

 fit would be somewhat tighter. (This analysis remains to be done.) It would still 

 be the case, however, that in the great majority of cases, predicted values fall 

 below the actual values of standing crop. 



