Spawning migrations and habitat use by fluvial westslope cutthroat and bull trout 

 in the upper Blackfoot Watershed 



Introduction 



Recently the seasonal movements and habitat use by fluvial westslope cutthroat 

 frout and bull trout have been studied in the lower Blackfoot River and its tributaries 

 (Swanberg 1997, Schmetterling 2001, 2003). These studies provide insight to fluvial life 

 history strategies, seasonal movements and habitat use by fluvial bull trout and westslope 

 cutthroat trout (WSCT)). Often, extensive migrations (>70 miles) to spawn in natal 

 tributaries are a component to fluvial life histories (Schmetterling 2001; Swanberg 1997). 

 Spawning often occurs at discrete locations in tributaries (Swanberg 1997, this report). 

 After spawning, the young rear in these tributaries for up to four years before migrating to 

 mainstem rivers to mature (Shepard et al 1984, Northcote 1992). Thus, tributaries that 

 are connected to the mainstem river, with habitats suitable for spawning and rearing are 

 critical for maintaining population of WSCT and bull trout (Swanberg 1997, 

 Schmetterling 2001. this report). 



Tributary inventories in the Blackfoot watershed have identified pervasive 

 alterations to tributaries at the low-to mid elevations of the watershed with 85 of 90 

 inventoried streams identified as fisheries-impaired (Pierce et al. 2002b). This level of 

 tributary alteration contributes not only to population declines at a broad level; it also 

 necessitates expansive tributary restoration as a primary method of native species 

 conservation and recovery. 



To begin a transition of expanding restoration to the upper Blackfoot Watershed, 

 in 1999 the Montana Fish, Wildlife and Parks began a 3-year fisheries inventory and 

 problem identification study on 49 tributaries in the upper watershed upstream of the 

 North Fork confluence (Pierce et al. 2002, 2001 and 2000). These studies identified: 1) 

 the widespread distribution of non-introgressed WSCT in tributaries; 2) precariously low 

 bull trout densities; and 3) impairment on 46 of 49 inventoried tributaries, with 

 significantly lower densities of native fish in the lower reaches of most tributaries 

 compared with upstream reaches. Reduced population densities result fi"om 

 environmental variables such as natural stream dewatering, as well as anthropogenic 

 sources such as habitat alterations and degradation, entrainment in irrigation ditches, 

 irrigation dewatering, and barriers to movement and non-native species interactions 

 (Pierce et al. 2002, 2001 and 2000). 



Expanding on these upper basin studies and in order to determine 1) patterns of 

 movement and behavior of bull trout and westslope cutthroat trout; 2) identify tributaries 

 where fluvial bull and WSCT spawn; 3) 4) identify restoration opportunities in tributaries 

 supporting fluvial native fish; and 5) provide information necessary for fiiture funding of 

 identified restoration opportunities, we conducted a radio telemetry study of fluvial bull 

 trout and WSCT captured in a 54.9 miles reach of the upper Blackfoot River between the 

 North Fork and Lincoln. The habitat features of this upper Blackfoot River differ 

 substantially fi-om the lower river, and this upper reach has received no use of radioed fish 

 in previous lower river studies. The goal of this study is foster restoration and the 



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