no 



efficiency would be expected, the small number of recaptures indicates a 

 migrating population. 

 Red Rock River 



A trout population estimate for a 5500 ft section of the Red Rock 

 River, located approximately two miles upstream of the reservoir, was made 

 in August, 1969 (Table 12). Total numbers and biomass of age 1 and older 

 trout were 182/1000 ft and 135 lbs/1000 ft, respectively. Brown trout com- 

 prised 91 and 92% of the estimated number and biomass of trout, respectively. 

 Mountain whitefish and longnose suckers were abundant, but were not 

 quantitatively sampled. Tagging results indicate trout movement does occur. 

 Within one year, two tagged trout from this section were caught in the 

 reservoir, another had moved through the reservoir and was caught seven 

 miles downstream in the Beaverhead River, and one was captured ten miles 

 upstream from the section. 



A trout population estimate for a 6250 ft section of the Red Rock River, 

 located several miles upstream of the section sampled in 1969, was made 

 in June, 1974 (Table 13). Brown trout comprised 85 and 79% of the estimated 

 number and biomass of trout, respectively. The total number and biomass 

 of trout/1000 ft were 135 and 124%, respectively, of those estimated in 

 the downstream section in 1969. 



In 1961, a total of 128 rainbow and brown trout greater than 7 inches 

 and weighing 135 pounds were captured by electrofishing in 659 ft of the 

 Red Rock River, now inundated by the reservoir. This is 197 and 208 lbs/1000 

 ft by number and weight, respectively. An actual estimate would be higher, 

 since it is unlikely that all trout in the section were captured. Consider- 



