When the angle was increased to 90° the 2-foot width of electrical field 

 appeared to be consistently more effective than the 3 -foot field (fig. 7) . The 

 maximum difference in effectiveness occurred at an electrode spacing of 24 inches. 



The results when 2 -inch electrodes were substituted for 1/2 -inch electrodes 

 showed a decrease in the difference of effectiveness between the 2- and 3 -foot widths 

 of electrical field. At a 90° angle of electrical field the 2 -foot width was more 

 effective than the 3 -foot width of field; the greatest difference occurred at a 24 -inch 

 electrode spacing (fig. 8) . 



The effect of the angle of field is shown in Figures 9 and 10. There appears 

 to be little difference in the effectiveness of the 40° and 60° angles of field with 

 two exceptions. One exception occurs at a 12 -inch electrode spacing, 2 -inch electrodes 

 and a 2 -foot width of electrical field; at tliis point the maximum percentage of finger- 

 lings was effected. Another exception occurs at a 6 -inch spacing, 2 -inch electrodes 

 and a 3 -foot width of field; the effectiveness is considerably less than the maximum 

 effectiveness but a significant difference exists between the 40° and 60° angles of 

 field. The 90° angle appears to be the least effective of the three angles of field. 



At a 40° angle with 1/2 -inch electrodes and a 2 -foot widtli of field the effective- 

 ness of electrode spacing increased between 6 and 12 inches and decreased to a spacing 

 of 36 inches (fig. 11). There appeared to be only a slight difference of effectiveness 

 at the 60* and 90° angles of field. An increase in the width of field to 3 feet and in the 

 diameter of the electrodes to 2 inches showed a similar result for the same angles 

 (fig. 12). 



There appears to be only a slight difference in effectiveness between 1/2 -inch 

 and 2-inch diameter electrodes. At a 40° angle of field and a 2-foot width of field 

 a significant difference exists between the two diameters at a 6 -inch electrode spacing 

 (fig. 13) . When the width of field was increased to 3 feet, the difference in effective- 

 ness was greater at a closer electrode spacing (fig. 14). At a 90° angle of field the 

 difference in effectiveness increases between an electrode spacing of 6 and 24 inches 

 and decreases at a 36-inch spacing (fig. 15). 



Preliminary tests were run under a maximum light intensity to investigate the 

 effect of light on the effectiveness. In one test the previously described procedure 

 was followed in which 60 fingerlings were released. At an angle of 40°, electrode 

 spacing 6 inches, a width of field of 2 feet and with 1/2 -inch electrodes a slight in- 

 crease occurred. When 200 fingerlings were released the effectiveness was again 

 increased. 



23 



