20 -I 



500 



600 700 800 



Fork Length (mm) 



900 



1000 



Figure 6. Comparison of the 1975 and 1976 shovel nose 

 sturgeon fork length frequencies (by percentage of catch) in 

 the Tongue River. 



In 1974, 427 shovelnose sturgeon captured in the Tongue River were 

 measured by Peterman and Haddix (1975). Since total lengths rather than fork 

 lengths were recorded in 1974, their results were converted by the regression 

 formula: 



TL = 110.109 + 0.938 FL 



where all measurements are in millimeters. The fork length range in 1974 was 

 449 mm (17.7 in) to 969 mm (38.1 in) with an average length of 700 mm 

 (27.6 in). 



The length frequency of shovelnose sturgeon sampled downstream from the 

 Intake Diversion on the Yellowstone River in the spring of 1975 was plotted 

 and compared to the Tongue River sample for the same time period (Peterman 

 and Haddix 1^75). Yellowstone River sturgeon ranged from 287-815 mm (11.3- 

 32.1 in), with an average length of 508 mm (20.0 in). More than 50 percent 

 of the sample fell in the size class 330-480 mm (13.0-19.0 in) with the modal 

 interval of 386-404 mm (15.2-15.9 in). The length-frequency distribution of the 

 Tongue River sample is compared to the Intake sample in figure 7. Sturgeon 



27 



