the vast majority of eggs collected were determined to be from 

 walleye (see Distribution of Eggs) . The depths at which eggs were 

 collected ranged from 30 to 107 cm (1.0 to 3.5 ft.). The minimum 

 depth at which eggs were collected from the Intake gravel bar, 30 

 cm, was identical during each of the three years. In a lake 

 environment walleye spawned at depths between 30 and 76 cm (Priegel 

 1970, Johnson 1961). Nelson (1968a) found sauger eggs at depths of 

 61 to 365 cm in the Missouri River. 



Eggs were generally collected in deeper sites in 1977 and 

 shallower sites in 1979 with 1978 intermediate (Figure 25) . In 

 1977, 1978 and 1979; 71, 48, and 30 percent of the eggs, 

 respectively, were collected in water 76 cm (2.5 ft) or deeper. 

 Any one egg would be expected to occur in 46, 32, and 38 cm of 

 water or deeper 90% of the time in 1977, 1978, and 1979, 

 respectively. Since only depths up to 107 cm (3.5 ft.) could be 

 sampled, upper limits could not be calculated. 



The maximum velocity at which eggs would be expected to occur 

 at a 90% confidence level was almost identical all three years, 94 

 to 96 cm/s (Table 21) . Perhaps this is the maximum velocity at 

 which walleye (sauger) can orient themselves during the spawning 

 act and/or at which eggs do not get swept away. 



Because the Yellowstone River carries large amounts of silt 

 during periods of runoff, a clean cobble or pebble substrate is 

 only present in areas with enough current to keep these fine 



85 



