Tributary Trout Spawning Migrations 



In an effort to evaluate spawning periodicity and 

 sources of trout recruitment in the middle Clark Fork, the 

 lower reaches of several tributaries were electrof ished or 

 set with traps during trout spawning periods to locate 

 spawning migrants from the Clark Fork. 



Most members of the trout family migrate during the 

 spawning season in search of suitable spawning sites (Hubbs 

 and Lagler 1970) . Spawning movements of lake dwelling 

 salmonid populations into inlet or outlet streams have been 

 extensively documented for rainbow (Rayner 1942; Hartman et 

 al. 1962; Calhoun 1966; Scott and Crossman 1973) and brown 

 trout (Fenderson 1958; Stuart 1957) and mountain whitefish 

 (Snyder 1918; Calhoun 1966). 



Less information is available on spawning movements of 

 river-dwelling salmonid populations into feeder streams. 

 Calhoun (1966) reported that resident rainbow trout popula- 

 tions in streams tend to move upstream, and if possible into 

 tributaries to spawn. River-dwelling brown trout in Ontario 

 normally seek tributary streams for spawning purposes (MacKay 

 1963) . Spawning movements of mountain whitefish from larger 

 streams into some tributaries have been observed in Montana 

 (Liebelt 1970; Brown 1971). 



Electrof ishing and fish trapping surveys indicate 

 considerable numbers of rainbow, brown, and westslope 

 cutthroat trout migrate from the Clark Fork into tributaries 

 to spawn (Berg 1986a) . Significant trout fry outmigrations 

 from several tributaries, monitored with fry traps, indicated 

 tributaries provide considerable recruitment of juvenile 

 trout to the Clark Fork (Table 2-20) . 



Lower Clark Fork Fishery (Flathead River to Lake Pend Oreille) 



Fish species composition in the lower Clark Fork has 

 been significantly altered by habitat changes and the 

 introduction of new species. Of the ten game species found 

 in the lower Clark Fork, only the westslope cutthroat, bull 

 trout, and mountain whitefish are endemic. Six game species 

 introduced since the impoundment of the reservoirs are 

 northern pike, black crappie, burbot or ling, kokanee salmon, 

 silver salmon, and smallmouth bass. Northern pike and black 

 crappie resulted from illegal introductions while the other 

 four species were planned introductions by DFWP. Of the ten 

 nongame fish species, only the bullhead, pumpkinseed, and 

 perch were introduced by man. 



2-35 



