Table 1. --Water temperatures and water resistivities at Tamarack Falls, Cascade Reservoir, 



Idaho, July U to Aug. 1, 1958 



this hypothesis, we required intervals when 

 the power was on and when it was off. We then 

 expected, if the hypothesis were true, to obtain 

 equal catches in the traps under each power 

 condition. A valid test would require, however, 

 that equal numbers of fish be available to the 

 installation when the power was on and when 

 it was off. To satisfy this requirement we 

 designed an experiment in which the power 

 condition ("on" or "off") was alternated for 

 successive 24-hour intervals between July 2 

 and August 1. 



TESTING THE INSTALLATION 



The experimental installation at Cascade 

 Reservoir, as used to test the hypothesis, was 

 built in June and tested from Jxily 2 to Aug. 1, 

 The testing began at 10:00 a.m., July 2, and 



continued through 10:00 a.m., Aug. 1. During 

 this testing, electrical conditions maintained 

 continuously over a 24-hour period were fol- 

 lowed by a 24-hour period of "power off." 

 Thus 15 days with "power on" were alternated 

 with 15 days with "power off." Three sets of 

 electrical conditions of varied pulse frequency, 

 pulse duration, and voltage were used as shown 

 in table 2, and one set (pulse frequency, 10 

 pulses per second; pulse duration, 50 msec; 

 and voltage, 180 v.) was repeated. Thus four 

 series of tests were made. Several species of 

 fishes besides squawfish were caught in the 

 traps, but only records of squawfish were 

 kept (table 2). 



Figure 7, prepared from table 2, shows the 

 catches for each 48-hour test of 24 hours 

 "power on" and 24 hours "power off" ex- 

 pressed as percentages of the total 48-hour 

 catch. In figure 7, each test period started at 



