or movement) in the size group of rainbows 4.0 to 10.9 inches. 

 The Johnsrud section carries slightly more (24%) 4.0 to 10.9 

 inches rainbows as Rock Creek, but only 55% of the numbers of 

 rainbows 11.0 to 13.9 inches found in Rock creek (Figure 10). in 

 addition, Rock Creek carries 30.4 rainbows/1,000 ft larger than 

 14 inches, compared to approximately 2.6 rainbows/ 1 , 000 ft in the 

 Johnsrud section. 



The Blackfoot river along with Rock Creek and the Clark Fork 

 River contain small populations of large fluvial bull trout 

 (Table 4). The best population of large adult fish appears to 

 reside in the Blackfoot River. Due to the extremely low density 

 of the large adult fish estimates are difficult to obtain. 

 However based upon available population sampling data the 

 estimated density in the Johnsrud section was only two adult fish 

 per mile in 1985 (Table 5) . 



Westslope cutthroat trout account for 9% of the estimated 

 trout population in this reach. Several tributaries to the 

 Blackfoot River in reach 5 contain good cutthroat populations. 



YOUNG-OF-THE-YEAR SAMPLING 



Young-of -the-year (YOY) densities were sampled at 53 

 selected sites throughout the Blackfoot river from the near the 

 mouth to Aspen Grove Campground near Lincoln (RM 117.6). This 

 survey was conducted to assess trout recruitment trends 

 throughout the drainage. Major tributaries were also sampled. 



Species composition of rainbow trout and brown trout YOY 

 were similar to trends in species composition observed during 

 sampling of adult trout in the Blackfoot River (Figure 14). The 

 presence/absence of YOY, therefore, appears to have a significant 

 influence on the species composition and abundance of adult trout 

 observed in the Blackfoot River. 



Reach 1: Headwaters to Lincoln 



Cutthroat and brook trout YOY were captured in three of the 

 five sections sampled in reach 1. No YOY were observed at the 

 Aspen Grove campground. Rainbow and bull trout YOY were not 

 present in the five sections sampled in this reach. Brown trout 

 YOY were present just above the Stemple Bridge near Lincoln- 

 this location approximates the upstream boundary of the brown 

 trout distribution in the Blackfoot River. 



Reach 2: Lincoln to Nevada Creek 



Trout YOY were sampled at six locations in reach 2. Brown 

 trout represented 100% of the YOY catch in this reach 



27 



