(Keogh). 4.70 fish/trap (349 in 74 sets); section Ila (Orcutt's). 2.00 fish/trap 

 (24 in 12 sets); and section lib (S-H), 4.95 fish/trap (99 in 20 sets). Catch 

 rates in 1976 were lower, averaging only 2.34 fish/trap (138 catfish in 

 59 trap sets). Traps were fished in sections lb and lib in 1976; catch rates 

 were the same in the two sections. Reduced flow levels and unusually high 

 suimer temperatures probably resulted in the lower catch rates. 



TAGGING STUDIES 



A total of 397 catfish were tagged in 1975, and 103 were tagged in 1976. 



Tag returns in subsequent trap sets averaged 6.3 percent in 1975 and 3.9 

 percent in 1976. Anglers returned 3.6 percent of the channel catfish tagged 



(18 of 500). Of those tagged in 1975, 5 (1.3 percent) were returned in 1975 



and 10 (2.5 percent)were returned in 1976 for a total return rate of 3.8 



percent. Only 3 (2.9 percent ) of the fish tagged in 1976 have been returned 

 by fishermen. 



Movements of fish tagged in the Tongue River were varied. Eight (44.4 

 percent) of the returned fish were returned from the Yellowstone River rather 

 than the Tongue River (table 18). Two of the fish tagged in 1975 and 

 recaptured in 1975 were caught in the Yellowstone. One fish was taken at the 

 confluence of the Yellowstone and Missouri rivers, about 303 km (188 mi) 

 downstream from where it was tagged. Only one of the fish recaptured in the 

 Yellowstone moved upstream after leaving the Tongue. Of the fish recaptured 

 in the Tongue River, 50.0 percent (5 of 10 fish) were recaptured in the 

 area where they were tagged. Four of these fish were recaptured the same 

 year they were tagged. All fish taken in the Tongue River that showed move- 

 ment showed upstream movement, but the eight that were returned from the 

 Yellowstone River obviously moved down the Tongue before entering the 

 Yellowstone. 



INSTREAM FLOW REQUIREMENTS OF INDICATOR SPECIES 



All fish, wildlife, and other aquatic organisms are dependent upon the 

 natural flow regimen of a river system. Fish production in rivers depends 

 upon the maintenance of spawning and rearing areas, sufficient shelter, 

 adequate food supply, and water quality. The stream discharge, as influenced 

 by channel configuration, must meet the hydrologic requirements necessary 

 to provide these factors. 



The State Water Planning Model simulated monthly streamflow conditions 

 which would result from the implementation of several levels of agricultural 

 or industrial development. Monthly Tongue River subbasin outflows and total 

 dissolved concentrations estimated by the model provided the basis for pre- 

 dicting impacts on the fisheries. Four levels of industrial and three 

 levels of irrigative withdrawals were considered. 



As explained on page 17 , potential impacts were assessed on the basis 

 of the effect on flows associated with three life-history stages of fish-- 

 passage, spawning, and rearing. 



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