The following results of the systematic tests 

 are summarized in table 4: 



1. Electrode array C appeared to be the most 

 effective at all three voltage gradients: 85,93, 

 and 96 percent of the fish, respectively, were 

 prevented from passing through the electrical 

 field. 



2. Electrode array D produced the most 

 variable response in the adult squawfish at 

 different voltage gradients. The percentages of 

 adult squawfish that were prevented from 

 passing through the electrical field were 58 

 percent at 0.75 volts/cm., 86 percent at 1.00, 

 and 96 percent at 1.25. Electrode array D was 

 thus as effective as electrode array C at the 

 voltage gradient of 1.25 volts/cm. 



3. Electrode arrays E and F produced 

 similar responses in adult squawfish, and both 

 were generally less effective than C (except for 

 array F at 1.25 volts/cm.). 



(4) Effectiveness for all four arrays in- 

 creased with an increase in voltage gradient. 



The results of significance tests applied to 

 the data from experiments shown in table 4 

 were as follows (table 5): 



1. The effects of the voltage gradients tested 

 (0.75, 1.00, and 1.25 volts/cm.), for both par- 

 allel and staggered electrode arrays, were 

 significantly different at an electrode spacing 

 of 91 cm. (arrays D and F), but not at an 

 electrode spacing of 61 cm. (arrays C and E). 



2. With the staggered electrode array (C and 

 D), the effects of electrode spacings of 61 and 

 91 cm. were significantly different at voltage 

 gradients of 0.75 and 1.00 volts/cm., but with 

 the parallel array, the effects of these electrode 

 spacings were not significantly different at any 

 voltage gradient. 



3. Differences between electrode arrays C 

 and D and between arrays D and F were not 

 significant at any of the three voltage gradients 

 or at either of the two electrode spacings. 



CONCLUSIONS 



The staggered array of electrodes--C, with 

 electrodes spaced 61 cm. apart in each row 

 and supplied with capacitor discharge pulses 

 at a rate of 8 per second and a duration equiv- 

 alent to that of a 40 msec, "rectangular" 

 pulse- -provided the most effective electrical 

 conditions. Under these conditions 85, 93, and 

 96 percent of the adult squawfish were pre- 

 vented from passing through electrical fields 

 at voltage gradients of 0.75, 1.00, and 1.25 

 volts/cm. respectively. 



The results reported in this paper are 

 necessarily of an exploratory nature; the tests 

 were performed under limitations of time, 

 numbers of fish, and storage facilities for the 

 fish. The data would be improved by (1) an 



increase in the number of tests and of individual 

 fish in each test, (2) a larger range of sizes 

 of adult squawfish, and (3) the use of smaller 

 ranges of water temperature and resistivity. 

 Recommendation of an electrical barrier at 

 the entrance to Drano Lake as a field site would 

 necessarily depend upon successful experi- 

 mental demonstration of the effectiveness of 



Table 4. — Results of indicated systematic tests on the 

 effectiveness of various electrode arrays combined 

 with electrical conditions of set II in blocking 

 adult northern squawfish (10 fish in each test) 



Table 5. — Significance tests on experiments (table 4) in blocking 

 adult northern squawfish with electrical fields 1 



1 These tests were applied to percentaj 

 tion to: angle ■ arc sin V percentage I 



;e data after transforma- 

 Snedecor, 1950). 



