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habitat usage. Subsurface ice can also play an important 

 role by obliterating typical fish habitats and flooding and 

 dewatering others. This forces fish to utilize whatever 

 habitat remains regardless of its suitability. 



Winter Activity of Trout 



Maciolek and Needham (1952) and Needham and Jones (1959) 

 observed actively feeding trout in California mountain 

 streams throughout the winter when water temperatures were 

 at or near freezing. In the latter study, trout also 

 defended territories during the winter. I 



These findings dispute the commonly held opinion that 

 wintering trout in mountain streams are indifferent to food 

 and exist in a torpid or inactive state. Other 

 observations, such as young salmonids entering the substrate 

 in winter and juveniles showing a stronger association with 

 the bottom in winter than during warmer months, demonstrate 

 that in some situations fish are less active in winter. 





winter Water Availability in Montana 



^■' . - J^S _ .H !V' -1 t U iA O 



Unlike regions of the U.S. having greater rainfall, monthly 

 stream flows in the mountain streams of Montana are almost 

 totally dependent on the annual snowpack. As a result, 

 streams exhibit two distinct flow periods; a relatively 



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