this time large numbers of ripe sauger were present in the Tongue 

 and Powder rivers (Figures 4 and 5) . Only 116 mature sauger were 

 collected in this 272 km section of the Yellowstone River (Figure 

 11). The catch rate for all mature sauger was only 0.4 fish/km. 

 The greatest concentrations of fish were near the mouth of the 

 Tongue and Powder rivers. 



The small number of mature sauger (particularly males) found 

 throughout the Yellowstone River during the spawning period 

 suggests that sauger spawning was less concentrated in the mainstem 

 than in the lower Tongue and Powder rivers. 



Sex ratios (male: female) of mature sauger collected in the 

 Tongue River were always weighed towards males, ranging from 2 : 1 to 

 89:1. Sex ratios in the Powder River were, except on two 

 instances, weighted towards males. The sex ratios for all mature 

 fish collected from the Powder (n=573) and Tongue (n=2637) rivers 

 during 1976 through 1980 were 9:1 for both tributaries. Sex ratios 

 in the Yellowstone River at the onset of spawning (the day the 

 first ripe or spent female was collected) with few exceptions were 

 weighted towards females, usually 1:2 or less. 



The preponderance of males in the Tongue and Powder rivers 

 during the spawning period suggest these two tributaries are 

 important spawning areas for this species. Preigel (1970) found 

 males comprised 70 to 90 percent of mature walleye captured on 

 tributary spawning grounds to Lake Winnebago, Wisconsin. In 

 contrast, the general paucity of male sauger in the Yellowstone 

 River suggests that spawning is more dispersed in the mainstem. 



29 



