and Yellowstone cutthroat trout, overharvest and competition with introduced brook trout 

 and brown trout (Likncs 1984; Allendorf and Leary 1988; Liknes and Graham 1988; 

 Mclntyre and Rieman 1995; Shepard et al. 2003). In the Blackfoot Watershed, WSCT 

 occupy -93% of historical range, compared with -39% of occupied historical range 

 statewide. The Blackfoot River also supports one of the larger fluvial meta-populations 

 of genetically unaltered WSCT (upper drainage) in Montana, but at population abundance 

 well below habitat capacity (Shepard et al. 2003). 



The Blackfoot River watershed (outside of the Clearwater Drainage) supports a 

 nearly basin-wide distribution of WSCT with 86% (84 of 98) of surveyed fish-bearing 

 tributaries containing WSCT (Pierce et al. 1997, 2002, 2001, Pierce and Schmetterling 

 1999, Peters 1990, Results Part IV). Streams lacking WSCT are either impau-ed 

 headwater streams or degraded spring creeks. Outside of the Clearwater River drainage. 

 WSCT stocks include migratory [fluvial) and non-migratory (resident) fish. Fluvial fish 

 have a sympatric resident component. Both resident and fluvial WSCT rely on high 

 quality tributary habitats for spavraing, rearing and over-wintering, and both often inhabit 

 the same stream. Resident fish can also maintain populations in isolation, occupying less 

 than one mile of perennial stream in some cases (Pierce et al. 2001), whereas access to 

 the Blackfoot River is also necessary for fluvial fish (Results Part IV). Fluvial WSCT 

 spend early life stages in smaller streams, migrate to rivers at age 2-3 where they mature 

 and grow to much larger size than resident fish, before returning to natal tributaries at - 

 age 5 to spawn (Behnke 1992). 



In Montana, 



only 8 - 20% of the 

 historical range is 

 occupied by genetically 

 unaltered fish (Shepard 

 et al. 2003). By 

 contrast, WSCT genetic 

 tests in the Blackfoot 

 watershed show a high 

 degree of genetic purity 

 over large areas of the 

 watershed, particularly 

 in the upper watershed 

 upstream of the 

 confluence of the North 

 Fork (Figure 6). For the 

 watershed as a whole, 

 52 of 72 (72%) streams 

 tested for introgression 

 supported unaltered 

 WSCT stocks. Twenty 

 five percent (n=17) of tested streams ranged from 90 - 99.9% unaltered, and 4% (n=3) of 



Figure 6. WSCT genetic samples sites and results tor 72 tributaries of the 

 Blackfoot Watershed (MRIS 2003, FWP files, this report). 



tested streams were <90% introgressed (Figure 6). 

 utilized the entire Blackfoot River (Schmetterling 2001 



Telemetry studies show WSCT 

 , Results Part IV). Introgression 



12 



