documented (Magee et al. 1996), but not in the lower Blackfoot where repeat migrants 

 did not spawn within 3.1 miles of their previous year's spawning location (Schmetterling 

 2001). This range of fidelity within the Blackfoot River watershed (low in the lower 

 basin and high in the upper basin) indicates that spawning sites may be more limiting in 

 the upper drainage than in the lower drainage. Lower densities of WSCT in the upper 

 drainage compared with the lower drainage seem to support this premise. We also found 

 higher fidelity to wintering sites with 40% of post-spawning fish returning to their 

 original capture locations, compared with 11% in the lower river study. These 

 differences may relate to the quality of wintering pools in the upper drainage compared 

 with the lower drainage where pools are larger. In our study, we observed wintering in 

 larger pools. 



Although we did not analyze the extent of intermittent reaches between the upper 

 and lower drainages, a majority of WSCT (62%) ascended intermittent reaches to access 

 upstream spawning sites in our study, compared with 4% of WSCT utilizing spawning 

 streams identified in an earlier study (Schmetterling 2001). All telemetered WSCT 

 migrating downstream through intermittent reaches returned during non-base flow 

 periods. Mortality did not appear to be directly related to intermittent reaches, a problem 

 affecting out-migrant bull trout during base flow migration periods (Swanberg and Bums 

 1997; Pierce et al. 2001), indicating a highly selective adaptations to intermittent channels 

 for WSCT. 



This study outlines the importance of pools and LWD as an important habitat 

 features. WSCT not only occupied for pools a majority of the time (despite low 

 availability in some areas), they were also "cover-oriented" at all locations regardless of 

 the channel type or location within a habitat unit. Implications with pool and cover 

 associations relate to certain land management (unregulated riparian grazing and timber 

 harvest), which potentially influence the integrity of stream banks, overhanging 

 vegetation, and recruitment of LWD, more so in alluvial (C-type) channels, which are 

 more subject to stream bank damage, channel widening and subsequent loss of cover than 

 geologically controlled (B and F-type) channels (Rosgen 1996). Adverse alterations of 

 WSCT habitat in (C-type charmels) occurs in the middle and upper reaches of the study 

 area (Marler 1997; Confluence 2003) and is extensive in tributaries with comparable 

 alluvial valley bottoms (Pierce et al. 2002b). 



The high post-spawning mortality and predation by avians observed in this study 

 suggests WSCT are vulnerable in tributaries, especially during low-water years, which 

 has been confirmed in other studies (Brown and Mackay 1995; Schmetterling 2001). In 

 our study, we found nine of 11 (82%) WSCT known mortality sources occurred by 

 predators and the remaining two were illegally harvested. Of avian predation, 50% (4 of 

 8) of the WSCT mortality was traced to a single heron rookery near the mouth of Nevada 

 Creek. The distance from kill sites to the rookery extended from 0.5 to 19.5 air miles. 

 Vulnerability to heron predation may be elevated in part due to extensive riparian and 

 channel alterations that have widened channels and reduced cover in many streams in the 

 alluvial bottomlands near Nevada Creek. 



Restoration and management implications 



76 



