rainbow trout per mile in the Clark Fork during a three-year 

 period from 1984 to 1986 (Tables 2-17 and 2-18) . The com- 

 parison of the Blackfoot River with the Clark Fork is 

 appropriate because both rivers have similar physical habitat 

 characteristics . 



Catchable trout 7 inches total length and larger. 

 Source: Berg 1986a. 



Scales were collected from trout during population 

 samplings to determine growth rates and age structure of the 

 trout populations. Preliminary findings indicate growth 

 rates of trout in the Clark Fork are relatively high when 

 compared with trout streams of similar size. This indicates 

 that food supply is probably not a limiting factor for trout 

 populations in the Clark Fork. Furthermore, it suggests that 

 the Clark Fork may be "under seeded" and that recruitment may 

 be a limiting factor. 



Trout Spawning and Rearing Habitat 



Visual surveys have been made in the Milltown, Missoula, 

 Huson, and Superior study sections during the rainbow and 

 brown trout spawning periods in an attempt to locate trout 

 redds. To date, only brown trout redds have been located, in 

 the Milltown and Missoula sections. Because a very limited 

 amount of time has been spent on visual surveys, additional 

 observations must be made to evaluate the extent of trout 

 spawning in the river. 



2-33 



