The following equation, with a correlation of r = 0.8355 (figure 10), was 

 derived: 



log w = 3.3439 log fl - 6.2339 



where: w = weight in grams 



fl = fork length in millimeters 



Zweiacker (1967) found a length-weight relationship for Missouri River 

 shovel nose sturgeon of: 



log w = 2.79128 log fl + 0.68145 



Helms (1974) reported the length-weight relationships of two pools (17 and 19) 

 on the Mississippi River to be, respectively: 



log w = 3.526 log fl - 2.2632 



and 



log w = 3.083 log fl - 2.3136 



All the above length-weight relationship equations have similar slopes; 

 the major difference between the Tongue River equation and the others is the 

 constant, which is indicative of the larger size of the population migrating 

 into the Tongue River to spawn. 



A size difference was shown between males and females. Males were 

 smaller, averaging 733 mm (29.1 in) with a range of 523-864 mm (21.0-34.0 in) 

 in 1975 and 760 mm (29.9 in) with a range of 592-934 mm (23.3-36.7 in) 

 in 1976. In 1975, females averaged 806 mm (31.7 in), ranging from 688 mm 

 to 937 mm (27.1 to 36.9 in); in 1976, they averaged 832 mm (32.8 in), 

 ranging from 592 irni to 934 mm (23.3-36.7 in). Weight differences were 

 more apparent, with males averaging 1.95 kg (4.30 lb) in 1975 and 2.17 kg 

 (4.78 lb) in 1976, while females averaged 3.20 kg (7.05 lb) and 3.62 kg 

 (7.97 lb), respectively. 



Size at Maturity 



Since sexual dimorphism is absent in shovelnose sturgeon, sex determination 

 was accomplished in two ways. Slight pressure exerted on the abdomen pro- 

 duced milt or eggs if the fish were nearing spawning condition. If repro- 

 ductive products were not produced, sex was distinguished by dist nsion of 

 the ovarian region and by the swelling of the ovipositor. If none of the 

 criteria were met, fish were recorded as undesignated sex. These methods 

 have been used to determine sex rations for other species (Snow 1963 and 

 Casselman 1974). Observed sex ratios for males, females, and undesignated 

 were 46.9, 12.9, and 40.2 percent, respectively, in 1975, and 63.6, 8.4, and 

 28.0 percent respectively, in 1976. The high incidence of undistinguishable 

 fish probably tends to mask the true sex ratio. However, it appears that 

 more males enter the run than females, a situation also true of paddlefish 

 (Elser 1976). 



32 



