45,000 



TEST SERIES 



WATER RESISTIVITY 



(ohm cm.) 35,000 - 



25,000- 



WATER TEMPERATURE 

 CO 



20' 



15' 



rrm\m\ 



Voltoge 180 v. 



ELECTRICAL CONDITIONS Frequency 10 pulses/sec. 



Duration 50 msec. 



100 



I80v. 

 15 pulses /tec. 

 25 msec. 



140 V. 

 10 pulses/sec. 

 50 msec. 



iSOv. 



10 pulses/sec 



50 msec. 



ES POWER ON 

 ^ POWER OFF 



14 16 



JULY 



18 



20 22 



24 



26 



28 30 



Figure 7. — Percentage of squawflsh trapped with "power on" and with "power off" for each 48-hour test, July 2 to Aug. 1. 

 1958. Data on trapping of squawflsh are plotted against average daily water temperature and water resistivity. 



10:00 a.m. on the date shown and ended 48 

 hours later. Also shown in figure 7 are average 

 daily water resistivity and water temperature 

 readings. 



Table 3 was prepared to show the numbers 

 and percentages of squawfish taken in each 

 trap for the different conditions. One possible 

 explanation of the consistently greater numbers 

 of fish in trap No. Z during "power on" lies in 

 the response of the squawfish to the direction 

 of the positive charge of the sequentially 

 pulsed electrical fields. The electrical fields 

 in the electrode array were switched in the 

 direction of the apex away from trap No. 1 

 (west side of bridge, right bank), and this 

 switching continued in the direction of trap 

 No. Z (east side of bridge, left bank). It has 

 been demonstrated in the laboratory that 

 adult squawfish move toward the positive 

 charge (Maxfield, Liscom, and Lander, 1959). 

 The larger catches of squawfish in trap No. 2, 

 in comparison with catches in trap No. 1, may 

 have reflected this response. 



Table 4 groups the data of table 3 under the 

 different electrical conditions. We assumed 

 that equal numbers of fish were available when 

 the power was "on" and "off" within each test 

 series. The results suggest that the test con- 

 dition with voltage 180 v., pulse frequency 15 

 per second, and pulse duration 25 msec, was 

 less effective than the other electrical condi- 

 tions in diverting the northern squawfish into 

 traps. This result is also shown in figure 8. 



Under the hypothesis that the electrical 

 fields did not divert the fish into the traps, we 

 expected half of the total count in all traps to 

 be taken during each power condition. The total 

 catches were as follows (table 4): 



Power condition 



Power on 

 Power off 

 Expected (in each trap) 



Total catch 



of squawfish 



Number 



354 

 110 

 232 



11 



