STUDY AREA AND METHODS 



Electrof ishing with three types of systems was onducted on 

 the Big Hole River and associated tributaries from June 21 to 

 August 28, 1989 to collect information on the distribution and 

 relative abundance of grayling and in an attempt to locate areas 

 with high densities of YOY Arctic grayling for later habitat 

 measurements. Ten sample sections (Fig. 1), ranging in length 

 from 0.18 to about 5 miles, were electrof ished from one to 

 several times. Streamflow discharge ranged from about 2 cubic 

 feet per second (CFS) in the smaller channels and tributaries in 

 late July and August to about 70 CFS in the mainstem of the Big 

 Hole River during high flows in late June (Table 1) . 



Two mobile electrode electrof ishing systems and a series of 

 stationary grid-type electrof ishing units were used throughout 

 the study. Three people operated the boat system, which 

 consisted of a plastic flat-bottom boat (Coleman Crawdad model) 

 equipped with a 120 volt gasoline-powered generator and a Harvey 

 Leach rectifying unit with an attached negative electrode and 

 mobile positive electrode. A Coffelt BP-IC backpack 

 electrof ishing system was used in areas where the boat system was 

 not applicable (where the water was too shallow) . Electrof ishing 

 grids were constructed to sample microhabitat utilization by YOY 

 grayling in a manner similar to that described by Bain et al. 

 (1985) . All electrof ishing systems were operated with direct 

 (DC) , non-pulsed current ranging from 75 to 500 watts. The boat 

 system was used early in the season when higher discharges were 

 present and for the majority of the sampling on Swamp Creek 

 (sections A and B) and the Big Hole River proper (sections C,D, 

 and E) where flows were seldom below 10 CFS. Electrof ishing 

 always proceeded downstream with the boat system, as the primary 

 purpose in using the boat system was to quantify distribution and 

 relative abundance of fishes and habitat measurements were not 

 made in areas that were sampled with only the boat system. 



