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the primary food of stream trout. Sufficient food must be 

 available to allow the trout to recover from the rigors of 

 winter and begin to grow when the water warms and fish 

 metabolism increases. Trout survival will be affected if 

 the spring rise in water temperature is not accompanied by 

 an increase in food. 



A less important function of the food producing area in 

 winter is to supply food for wintering trout. While the 

 scarcity or unavailability of food is only considered a 

 secondary cause of winter mortality, it can be important 

 during those winters in which the physical condition of the 

 environment is so degraded by ice as to be barely tolerable 

 to trout. 



The naturally occurring low flows of winter reduce the 

 amount of riffle habitat (the food producing area of 

 streams) to its lowest level of the year. Due to the wide, 

 shallow configuration of riffles, flow reductions affect 

 this habitat type much more severely than the deeper pools 

 and runs. Winter flow levels alone, particularly during 

 below normal water years, can affect the food supply through 

 its influence on the amount of riffle habitat that is 

 available to overwinter the bottom organisms. Ice action 

 can further deplete the food organisms by subjecting riffle 

 sections to sudden scouring and partial drying and freezing 



