years. Necessary duration of this flow is not known but is 

 suggested to be for a minimum of 24 hours (Peterman 1979) . 



SUMMARY 



Chronology of abundance of sauger, tag returns and 

 distribution of eggs and larvae show that the Tongue and Powder 

 rivers are two major spawning areas for this species in the 

 Yellowstone River system. Sauger larvae were captured in drift 

 nets in the Tongue and Powder rivers near their mouth, 

 demonstrating that successful reproduction is occurring in these 

 two tributaries. No larval sauger were caught in the Yellowstone 

 upstream from the Tongue River. Mature sauger were not abundant in 

 the mainstem between Forsyth (river km 381) and the North Dakota 

 border (river km 26) at a time when spawning concentrations were 

 evident in the Tongue and Powder rivers. Only downstream from 

 Intake diversion, river km 114, was sauger reproduction documented 

 in the mainstem of the Yellowstone River. However, this was also 

 a major walleye spawning area; sauger eggs comprised only 2 to 12 

 percent, depending on the year, of the combined walleye-sauger eggs 

 collected from this area. Loss of the Tongue and Powder rivers as 

 sauger spawning areas could eventually decrease sauger abundance in 

 the Yellowstone River if alternative spawning areas were not 

 utilized. 



Walleye are not numerous in the Yellowstone River except 

 during April and May when large numbers migrate out of Garrison 

 Reservoir (an impoundment on the Missouri River) and move upstream 

 into the Yellowstone River. A spawning area, which supported large 



101 



