it^.. 



composition (% of total catch for fish >6.0") in the Johnsrud section was 67.6 % rainbow 

 trout (n= 499), 18.7 % brown trout (n=138), 11.4% WSCT (n= 84) and 2.3% bull trout 

 (n=17). Based on the total trout point estimate (fish >6.0"), the total trout density 

 estimate for the Johnsrud section decreased slightly fi-om 134 to 129 fish/1000' a decline 

 of 4% between 2002 and 2004. Total trout biomass (fish >6.0") however declined 26% 

 fi-om 105 to 78 pounds/ 1000.' 



Densities of native WSCT (> 6.0") decreased slightly fi-om 15.2 to 13.9 fish/1000' 

 (Figure 10). Because of small sample size and a low recapture rate, we were unable to 

 generate a valid bull trout estimate, although catch statistics suggest a substantial decline. 

 The 2004 point estimate for brown trout (> 6.0") was static at 19.2 compared with 20.1 

 fish/1000' in 2002 (Figure 9). The density estimate for rainbow trout (>6.0") indicates a 

 slight decline of 88/1000' in 2004 compared to 94/1000' in 2002 (Figure 12). 



In 2004, we observed one northern pike in the Johnsrud section, compared with 

 two in 2002, six in 2000, two in 1998, one in 1996, and none prior to 1996. Our 

 observations of the clinical signs of whirling disease (cranial deformities) have increased 

 slightly fi-om 2002 to 2004 (Results Part IV). . 



; f f 



Scotty Brown Bridge section i^ ^ ■ ■' 



The 2004 percent trout composition for the total catch in the Scotty Brown Bridge 

 Section was 33.3% 



Density/1000' + 95% CI 



16 

 14 

 12 

 10 



rainbow trout (n=173), 

 24.2% brown trout 

 (n=126), 37.1% 



WSCT (n=193), 5.4 % 

 bull ti-out (n=28). Total 

 trout (fish >6.0") 

 densities decreased ~ 

 46% fi-om 89.9 to 48.7 

 fish/1000' between 

 2002 and 2004. Total 

 trout biomass (fish 

 >6.0") has declined 

 49% fi-om 94 to 48 

 pounds/1000' of River 

 between 2002 and 

 2004. 



Density 

 estimates for rainbow 

 trout (fish >6.0") are 

 shown in Figure 12. 

 Data show a significant recent decline for the species. This decline occurred within the 

 intermediate (1 1 .0-13.9) and larger (>14.0") size classes (Appendix C). Likewise, brown 

 trout (>6.0") showed a large decline fi-om 23.8 fish/1000' in 2002 to 9.6 fish/1000' in 

 2004 (Figure 9). Estimated bull ti-out densities (fish >6.0") also declined fi-om 5.1 to 2.4 

 fish/1000' between 2002 and 2004 (Figure II). WSCT densities (fish >6.0") also 

 decreased fi-om 20.3 to 17.8 fish/1000' between 2002 and 2004 (Figure 10). 



1990 1991 1993 1996 1998 2000 2002 2004 



Figure 11. Densities of bull trout (>6.0") in the Scotty Brown section of 

 the Blackfoot River, 1990-2004. 



23 



