was attributed to losses of preferred shoreline habitat during 

 low flow periods. Although the effects of a weak year class on 

 the adult population may not be detected immediately, there is 

 likely to be a gradual decline in adult numbers. 



Fisheries in this reach may also be adversely affected by 

 accumulation of fine sediments. Large amounts of sediment are 

 deposited in this reach due to its low gradient. Accumulation of 

 this sediment has probably increased because of the lack of 

 flushing flows that normally occur in the spring. Springtime 

 streamflows in the Blackfoot River have been below the 50% 

 exceedance level during each of the past five years, and visible 

 increases in streambed sediments is apparent. 



Metals contamination may also adversely effect the fishery 

 in this reach. Elevated levels of metals were observed in 

 streambed sediments of reach 2 in 1988, indicating that there has 

 been additional downstream penetration of contaminated sediments 

 that originated from previous mining activity in the headwaters 

 (J.Moore pers.comm.). In addition, elevated levels of cadmium in 

 the livers of large brown trout provide further evidence of 

 potential metals impacts in this stream segment. 



Although brown trout presently dominate the trout fishery in 

 this reach, brook trout were common in the Poorman-Dalton Section 

 during the early 1970 's. In 1972, there were an estimated 53 

 brook trout per 1,000 ft, but only a total of eight were captured 

 in 1988. It is not known whether this decline was a result of 

 changes in physical habitat, water quantity, water quality, or a 

 combination of these or other factors. 



Reach 3: Nevada Creek to Monture Creek 



The gradient of the Blackfoot River increases below the 

 mouth of Nevada Creek, and physical habitat characteristics 

 change abruptly in this reach of the river. Woody debris jams 

 are less common and meandering is less pronounced. Instream 

 cover in the form of rocks and boulders replace the undercut 

 banks and shoreline structural cover of reach 2. This is 

 probably the most scenic and isolated reach of the Blackfoot 

 River, but unfortunately, the lowest densities of trout reside in 

 this river segment. 



The trout population in this reach was surveyed in the 

 Raymond Bridge Section, located about six miles upstream from the 

 North Fork of the Blackfoot River. No fisheries surveys were 

 conducted in this reach prior to 1983. Although electrof ishing 

 efficiency in this section was high, too few trout were captured 

 to obtain an estimate of population density. Similar to reach 2, 

 brown trout are the dominant trout species, but rainbow and 

 cutthroat trout begin to appear in this area, comprising 20% and 

 9% of the raw catch, respectively. 



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