DISCUSSION 



The Blackfoot River is one of the most scenic and heavily 

 used river systems in western Montana. Users of this resource 

 have recently expressed concern that the river's fishery was 

 depressed and appeared to be declining further. Angler concerns 

 were substantiated after this first field season of fisheries 

 inventory - the Blackfoot River fishery indeed appears to be at a 

 level well below its potential. 



The potential problems, however, are complex and appear to 

 vary from one reach of the river to the next. Fine sediment 

 accumulation, low streamflows due to drought, metals toxicity 

 from previous mining activity, inadequate recruitment, 

 overharvest, and harsh winter conditions are among the many 

 problems that a given reach of the Blackfoot River encounters. 

 Five reaches were identified based on habitat characteristics and 

 attributes of the trout population within each river segment. 



Reach 1: Headwaters to Lincoln 



The Blackfoot River is relatively small stream in this reach 

 with base flows typically less than 20 cfs. Cutthroat and brook 

 trout are the dominate trout species present, comprising 53% and 

 46% of the trout population, respectively. 



Cutthroat trout densities have declined significantly in two 

 of the three electrof ishing sections located in this reach 

 compared to surveys conducted during the early 1970 's. In 1975 

 the tailings pond at the Mike Horse Mine breached sending metals 

 ladened sediments and water downstream into this reach. Fish 

 population sampling immediately after the dam failure in the 

 Flesher Section indicated a near total loss of YOY cutthroat, and 

 a significant loss of age I and older fish. In 1988, densities 

 of cutthroat in the Flesher Section remain below those observed 

 after the fish kill of 1975. Reductions in cutthroat density 

 were of a similar magnitude in the Below Pop's Place Section. 



Trends in brook trout densities were more difficult to 

 interpret. Differences between surveys during the early 1970 's 

 and the 1988 survey were not significant in Below Pop's Place 

 Section, but densities were dramatically reduced in 1988 at the 

 Flesher Section. These two sections are only about two miles 

 apart. Changes in physical habitat, particularly resulting from 

 beaver activity, is a possible explanation for the unpredictable 

 trends in the brook trout population. 



The Hogum Section, also located in this reach, provided 

 little information concerning population changes for cutthroat or 

 brook trout. Trout densities were low in the early 1970 's, and 

 remained low during the current survey. Available habitat in 



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