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prevents the supercooling of the stream. Anchor ice is 

 therefore more likely to form during periods of sparse snow 

 cover, such as early winter and in drought years. 



The work of the above authors indicates that sudden 

 catastrophes such as suffocation under collapsed snowbanks 

 or the dewatering of stream sections by ice dams are 

 primarily responsible for the high mortalities of stream 

 dwelling trout in winter. 



Trout Food Supply in Winter 



Winter is often thought of as a period when food is abundant 

 in trout streams. This belief is based on the fact that 

 most of the semi-aquatic insects that serve as the primary 

 food of stream trout overwinter on the stream bottom in 

 their immature stages before emerging as winged adults 

 during the warmer months. Logan (1961) found the bottom 

 food organisms to be abundant during the winter in Bridger 

 Creek, a small stream arising in the Bridger Mountains of 

 Montana. Convict Creek, California, supported higher 

 standing crops of aquatic food organisms during the winter 

 than in summer (Maciolek and Needham, 1952). 



The winter food supply can be depleted by ice action. 

 Reimers (1957) continued the bottom sampling program 

 initiated by Maciolek and Needham for Convict Creek and 



