Partridge 1980b). Almost all of the tagged sturgeon captured by Idaho Fish and 

 ™ Game personnel have shown movement (see Table 3). Sturgeon move in the river 

 between Kootenai Falls and Bonner's Ferry, Idaho, and from Kootenay Lake 

 upstream into Idaho (Partridge 1980b) (appendix D) . The purpose of this 

 movement is not known. However, sturgeon probably spawn over rocky or bedrock 

 substrates in swift current near rapids when water temperatures are between 8.9 

 and 16.7 degrees C. (48-62 degrees F) (Scott and Crossman 1973). It is 

 suspected that sturgeon from Idaho and British Columbia spawn or once did spawn 

 just below Kootenai Falls (Graham 1981). The river channel immediately below 

 the falls is bedrock with some gravel. Currents are swift even at depth because 

 the canyon is narrow and the gradient relatively steep. 



Spawning migrations of stream fish usually are triggered by one or a 

 combination of stimuli, including volume and temperature of the water, and the 

 length of the daylight period. Libby Dam has greatly altered flow regimes in 

 the Kootenai. Before the dam was built, high discharges during May and June 

 averaged 33,000 cfs. Now the flow during these months is 3,000 to 5,000 cfs. 

 This alteration of flow could have caused the decline of white sturgeon numbers 

 in Montana by greatly curtailing the spring spawning migration into Montana from 

 Idaho and British Columbia. At present, there are no dams to impede the 

 movement of white sturgeon between Kootenay Lake and Kootenai Falls. Sturgeon 

 do not use fish ladders on the Columbia or Snake River dams (Coon et al. 1977). 



In order to determine when and where sturgeon spawn in Idaho, the Idaho 



sturgeon study used a cone-shaped drift net to sample sturgeon larvae using 



techniques similar to those described by Kolhorst (1976). Sample time varied 



^ from 30 min. to one hour with one overnight set of 14 hours. Samples were 



taken once a week at the U.S. 95 bridge, Crossport, and Hemlock Bar from 25 



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