Of the 92 fish found in brook trout stomachs, 31 (34%) were 

 identified to species. Indices of Relative Importance and their 

 components for brook trout, rainbow trout, and burbot are located 

 in Tables 5, 6, and 7, respectively. Fish rank second or third 

 in relative importance in the diets of all three sample species. 

 Only one Arctic grayling YOY was positively identified in the 197 

 samples. The YOY grayling was found in the stomach of a 275 mm 

 brook trout captured in the large irrigation ditch on Cal Erb's 

 ranch (formerly the McDowell Ranch) near Wisdom. 



Another possible predator on YOY is the brown trout, a well 

 documented piscivore (Brown 1971) . Although found infrequently 

 in the upper portions of the Big Hole drainage, the brown trout 

 is quite common in the lower reaches of the Big Hole River (R. 

 Oswald, pers. comm.) If YOY Arctic grayling migrate downstream 

 in the fall, they may be preyed upon by brown trout. Such 

 predation by brown trout on YOY could be substantial and may play 

 a part in the large drop in YOY populations observed during their 

 first winter. Further study is necessary to address this issue. 



The results from the stomach content analyses indicate that 

 YOY Arctic grayling are not an important component in the diets 

 of the three species sampled. These results do not necessarily 

 indicate that predation on YOY grayling is not acting as a 

 limiting factor on YOY populations. Further sampling of stomach 

 contents, as well as a determination of YOY grayling availability 

 to possible predators are needed to determine whether or not 

 predation is really acting as a limiting factor. 



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