habitat is large rivers and lowland lakes, but channel cats are not tolerant 

 of pollution and require well oxygenated water. Spawning occurs from May 

 into July after water temperatures warm to 240C (75°F), with 26.70C (80°F) 

 reported as optimum spawning temperature (Brown 1971). Nests are usually 

 built in secluded, semidark areas around logs, undercut banks, or other 

 cavities. The channel catfish received game fish status in Montana in 1975 

 as the result of legislative action. 



FISH SIZE 



Length-Weight Relationships 



As shown in table 14, catfish taken in 1976 were smaller than fish taken 

 in 1975. 



TABLE 14. Average lengths and weights of catfish taken in the Tongue River in 



1975 and 1976. 



CONVERSIONS: 1 mm = .0394 in 

 1 g = .0022 lb 



Age and Growth 



In 1975, 337 spines were sectioned and aged; 132 were aged in 1976. The 

 1975 sample was divided into those catfish captured below the T&Y Diversion 

 (table 15) and those captured between the T&Y and S-H diversions (table 16). 

 Only fish sampled below the T&Y Diversion were analyzed in 1976 (table 17). 

 Ages were comparable between years for the section downstream from T&Y 

 Diversion. 



The variation of lengths in a year class increased considerably at 9 years 

 of age and greater in section lb and at 13 years of age and greater in 

 section lib in 1975. The average growth per year in section lb was 1.4 inches 

 per year; in section lib a pattern of strong growth every other year was 

 established. In the "good growth" years tne average was 1.6 inches; in the 

 "poor growth" years the average growth was 0.3 inches. 



55 



