concrete diversion dam, approximately 3 m high, spans the Tongue 

 River 32 km upstream from its mouth. This diversion prevents all 

 upstream fish movement. 



METHODS 



Walleye and sauger were sampled by electrof ishing from a 5.2 

 m flat bottomed aluminum boat powered by a 85 hp motor (Graham et 

 al 1979) . The electrode array was set up for pulsed direct current 

 as described by Novotony and Priegel (1974) . The power source was 

 a 2 2 0v, 3500W generator, with the output regulated by a variable 

 voltage pulsating unit (Coeffelt WP-10) . Output current ranged 

 from 10-15 amps at 100-200V. The pulse frequency was 80-100 pulses 

 per second and the pulse width was 50-80 percent. 



Total length of each fish was measured to the nearest mm and 

 weight was determined to the nearest 10 g. Sex of mature fish was 

 determined by the presence of sex products. For fish from which 

 sex products could not be extracted, a distended abdomen and 

 enlarged or inflamed genital area indicated a gravid female; 

 whereas a flaccid abdomen and inflamed genital area indicated a 

 spent female. All other fish were recorded as unknown sex. Fish 

 were tagged with numbered floy anchor tags, inserted near the 

 posterior base of the first dorsal fin. 



To determine relative abundance and monitor fish movements, 

 sampling stations were established in the Yellowstone River at: 

 Forsyth, mouth of Tongue River, mouth of Powder River, and 

 downstream from Intake diversion (Figure 3) . The Forsyth section 

 began immediately below an irrigation diversion and extended 



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