differences indicate more variability of fluvial life histories in the Blackfoot watershed as 

 a whole based on quantified differences between WSCT of the upper and lower 

 drainages. In addition, we also identified several fluvial spawning streams, along with 

 many problems influencing WSCT populations in spawning streams. Problems are 

 pervasive and involve culvert crossing, irrigation dewatering, entrainment to irrigation 

 ditches and habitat degradation (Pierce et al. 2002, 2001, 2000). 



Similar to previous studies, spawning movements of Blackfoot River fluvial 

 WSCT began just prior to the rising limb of the hydrograph, at which point adult fluvial 

 spawners moved up- and down river before entering spawning tributaries near the peak of 

 the hydrograph (Schmetterling 2001). Similar to the lower river study, WSCT spawning 

 in larger tributaries began movements earlier, migrated longer distances and remained in 

 larger tributaries significantly longer compared with WSCT spawning in smaller 

 tributaries. Repeat and alternate year spawning occurred and post-spawning mortality 

 was also high. Similar to this previous study, we failed to confirm mainstem spawning, 

 with one possible exception in an upper 3'^''-order section of the Blackfoot River, from a 

 fish that moved to the mouth of the previous years spawning tributary. 



Unlike other studies that showed more discrete use of lower-order streams (Magee 

 1996), our results were similar to the lower Blackfoot River study, as we identified 

 spawning sites in a wide range of sites that did not necessarily conform to any two- 

 dimensional geographical pattern. 



WSCT migration patterns appeared to be influenced by a degree of reach-related 

 variability in our study area. Mean starting date of the spawning migration incrementally 

 increased in the upstream direction fi-om April 27* in the lower reach, to April 30* 

 (middle reach) to May 3"^ in the upper reach, despite lower water temperatures (average 

 of 2° F, both years on April 27) in the lower reach compared with the upper reach. 

 WSCT migration distances also increased in the lower reach. Consistent with earlier 

 migrations and larger total pre-spawning movements, WSCT of the lower reach exhibited 

 longer duration (8 days) of pre-spawning movements (compared with the combined upper 

 reaches) and sustained substantially higher post-spawning mortality (64%) compared with 

 middle and upper reaches (combined total = 36%). Differences between the distance, 

 duration and mortality between the lower and upper reaches seem to relate to the 

 degraded conditions of tributaries and general lack of spawning site availability in the 

 lower reach. We identified extensive river movements (mean = 16.6 miles) of non- 

 spawning WSCT, compared with 3.6 miles in the lower drainage (Schmetterling 2001). 

 Comparing these movements with fish length between studies, we found no significant 

 differences (Maim-Whitney t-test, P==0.084). These movements further outline that 

 resource exploitation not only extends over broad areas of the river, but also varies 

 regionally within the watershed. Furthermore, unlike the previous study, we failed to 

 confirm relationships that smaller fish moved longer distances or moved earlier. 

 Schmetterling (2001) speculated this alternative finding was competition driven. If this is 

 the case, our finding would be consistent with this hypothesis given low salmonid 

 densiUes. Our study area would result in less competition, compared with the lower river 

 study where densities are much higher (Results Part II). 



We identified higher fidelity of adult WSCT to spawning and wintering sites, 

 compared with the lower study. High site fidelity for WSCT has previously been 



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