years. Numbers of juvenile brown trout were not estimated 

 during the 1987 survey due to the unsuitability of the gear 

 used, but numbers of brown trout smaller than 7.5 inches, 

 ages and 1, were recorded. In general, those numbers vary 

 in concert with adult population estimates. Highest numbers 

 of small (young) fish were observed in the Warm Springs area. 

 Numbers declined generally to a low near Bearmouth and 

 increased immediately upstream and downstream from the mouth 

 of Rock Creek. Except in the Warm Springs area, the numbers 

 of young trout were generally very low. 



During the summer of 1987, marked juvenile hatchery 

 rainbows were released in the low population areas below 

 Drummond. If these fish persist in the river, then it may 

 suggest that reproduction and juvenile survival is indeed a 

 major limitation on population levels. A few of those 

 stocked fish were recaptured by electrof ishing in the fall of 

 1987. 



Eggs and sperm were taken from brown trout spawners in 

 the Warm Springs area in 1987 and placed in the hatchery for 

 rearing. Fish reared from these eggs were marked and 

 released in the summer of 1988, and their survival will be 

 monitored in future years. Assessment of timing and 

 estimates of numbers of outmigrating juvenile brown trout 

 from spawning tributaries began in 1988 and will continue in 

 following years. 



Tributary Trout Spawning Migrations 



Tributary spawning habitats appear to be limited in the 

 upper river segment. Warm Springs Creek has been shown to 

 have a run of hundreds of brown trout during the spawning 

 season, and limited numbers of browns also enter Lost and 

 Racetrack creeks. The 1987 trapping of brown trout entering 

 the Little Blackfoot River yielded fewer than 400 trout, 

 which is far fewer than the Little Blackfoot appears capable 

 of supporting. A similar number of river migrants were 

 shocked in Gold Creek where access to trout is limited to 

 only 300 yards of stream due to an artificial barrier. The 

 importance of Flint Creek for spawning trout is unknown, but 

 spawning substrates there are of poor quality. Rock Creek is 

 no doubt a significant contributor to recruitment in the 

 Clark Fork, particularly for rainbow trout. 



In summary, available data are presently equivocal on 

 the questions of recruitment, available habitat, and rates of 

 trout mortality in river environments. However, the catch 

 from the Little Blackfoot spawning migration trap in fall 

 1987 may offer some clues regarding fish population dynamics 

 in the upper Clark Fork. Water quality and substrate 



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