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t 



velocities measured in shallow areas than for velocities measured 

 in pools. 



Transferability of utilization criteria to other streams 



It is desirable to know if the utilization criteria 

 developed in Table 6 can be transferred to other areas in the 

 upper Big Hole River drainage. Bovee (1986) provides two rules 

 regarding the tranferability of utilization criteria from one 

 stream to another. First, transferability is most appropriate if 

 the source stream has high diversity and the study stream has low 

 diversity; second, transferability is enhanced if the source and 

 study streams have similar habitat features. Both of the study 

 sites were considered to have fairly high diversity (in terms of 

 types and amounts of pools, riffles and runs, range of depths and 

 velocities, substrate types, amount of cover), but the relative 

 diversity of other streams in the upper Big Hole River drainage 

 is not known. With regard to similarity, there are numerous 

 habitat features these study sites lack that are found elsewhere 

 in the drainage. Rapids, boulders and high water velocities 

 (above 2 ft/s) are almost completely lacking in both study 

 sites — habitat features that are common in some locations in the 

 upper portions of the drainage. The streams also have few pools 

 over 4-5 ft deep, few areas dammed by beaver (which provide the 

 combination of deep, slow pools and overhanging bank cover) , and 

 very little debris — habitat features that are found in various 

 locations on the Big Hole River downstream from these areas. 

 Transferability based on similarity of habitat types may 

 therefore be somewhat limited. 



Bovee (1986) also feels that another useful technique for 

 reviewing transferability is convergence, whereby habitat 

 preference (or utilization) curves are developed on different 

 streams, and if the curves are similar, it helps to confirm that 

 the preference (or utilization) criteria respresent the species 

 throughout a geographical range. In this study, the habitat 

 utilization data from the Big Hole River were statistically 

 compared to similar information from Swamp Creek for the 

 possibility of convergence. Mann-Whitney rank tests (P = 0.05) 

 were used to to test the null hypothesis that median values for 

 habitat variables on both streams were the same. The null 

 hypothesis was not rejected for tests of depth, mean water 

 velocity, embeddedness, and all substrate types but cobble--but 

 was rejected for cobble and cover. The similarity between most 

 of the habitat variables for the two streams lends some support 

 to the potential for transferability to other streams in the 

 drainage. 



