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during the higher flow periods in July, while the backpack system 

 was used on the river during low flow periods in August and on 

 tributaries and irrigation ditches. Electrof ishing proceeded 

 downstream when the boat system was used, and proceeded either 

 upstream or downstream when the backpack system was used. 

 Electrof ishing sessions typically lasted 1/2 - 1 hour, and the 

 area covered during this time was referred to as a "sub-section." 

 Only Arctic grayling and trout were captured, and stunned fish 

 were placed in a live car until the end of the sub-section. 

 Lengths and weights of captured fish were measured to the nearest 

 0.1 inch (TL) and 0.01 pound, respectively. Scales were taken 

 from all age I and older Arctic grayling and rainbow trout, and 

 all fish over 8 inches TL were tagged with a floy anchor tag. In 

 some cases where brook trout densities were particularly high, 

 stunned brook trout were not captured, but instead were counted 

 and visually grouped into one of three categories: 1) 

 young-of-the-year (YOY) ; 2) under 6 inches TL, but not YOY ; and 

 3) over 6 inches TL. The relative abundance of other fish 

 species was also visually estimated for each sub-section, using 

 the following scale: "few" = 1-10 individuals, "some" = 11-25 

 individuals, "many" = 26-50 individuals, and "abundant" = 51+ 

 individuals. 



Although lengths and weights of fish were recorded in 

 English units, they were converted to metric units to make a 

 comparison with condition factors (K) generated by Liknes (1981) . 

 K values were determined using the equation: 



(W) (100,000) 

 K = 



L^ 



where W = weight in grams and L = length in millimeters. 



Macro- and microhabitat utilization by young-of-the-year 

 Arctic grayling was determined for the east channel of the Big 

 Hole River below the Wisdom Bridge (sample section H) and for 

 Swamp Creek (sample section J) • The objective of the 

 macrohabitat measurements was to characterize general stream 

 features with which the YOY fish were associated, including bank 

 height, stream width, pool and riffle size, and bank condition. 

 The objective of the microhabitat measurements was to 

 characterize depth, velocity, substrate, cover, and distance to 

 cover at the central part of the home range (focal points) of the 

 age 0+ fish. 



Focal points were determined during the normal process of 

 the electrof ishing surveys. The backpack electrof ishing system 

 was used, typically operated at 100-150 watts by a two- or 

 three-man crew. The typical approach was to walk in the water 

 (working either upstream or downstream) , with the person 



