conditions in the Little Blackfoot seem to be well suited to 

 brown trout reproduction, and upstream migrants should have 

 access to more than 30 miles of stream. The available 

 spawning habitat would appear to easily accommodate several 

 thousand fish. This suggests that factors controlling fish 

 populations in the mainstem are limiting available spawners 

 to numbers below the available spawning habitat capacity. 



Middle Clark Fork Fishery (Milltown Dam to Flathead River) 



Fish Species Composition 



The bulk of the sport fishery in this 119.4-mile reach 

 of the river is provided by rainbow trout along with a few 

 brown, bull, and westslope cutthroat trout. Mountain 

 whitefish provide an important winter sport fishery. Common 

 nongame fish species found in the reach include squawfish, 

 redside shiners, longnose dace, coarsescale suckers, and 

 slimy sculpins. 



Trout Population Estimates 



Trout populations have been estimated by electrof ishing 

 and mark/ recapture procedures in four study sections on the 

 middle Clark Fork. The study sections are located in the 

 vicinities of Milltown Dam, Missoula, Huson, and Superior 

 (Table 2-16) . Estimates in the four study sections indicate 

 the river supports from 175 to 402 catchable rainbow trout 

 per mile (Table 2-17) . Rainbow trout constituted more than 

 90 percent of the catchable trout population in all of the 

 study sections. Catchable brown, westslope cutthroat, and 

 bull trout were present in the river, but their numbers were 

 usually too low to estimate. In September 1986, estimates 

 of 16 catchable brown and 22 catchable westslope cutthroat 

 trout per mile were obtained in the Missoula study section. 



The density of catchable trout is less than expected 

 for comparable trout streams the size of the Clark Fork. 

 While the Clark Fork supports an average of 200 to 400 

 catchable trout per mile, other large trout rivers in Montana 

 often support 2,000 to 3,000 or more catchable trout per mile 

 (Berg 1984) . 



Major tributaries to the Clark Fork support larger 

 populations of catchable trout than the mainstem of the 

 river. The mean number of catchable rainbow trout per mile 

 in the Blackfoot River over a three-year period from 1983 to 

 1985 was 445 percent larger than the mean number of catchable 



2-31 



