.•5 



Figure 2. --Site No. 2 Installation, showing salmon migration path and positions of positive and negative electrodes. Dotted lines 

 indicate approximate depth contours (in feet). G, generator; P, pulser and control unit; O, operator with on-off switch and long- 

 handled dip-net. 



as the fish approached the eddy. The fast 

 current in the main part of the river 

 caused the fish to follow a narrow path, 

 3 to 5 feet wide, about 10 feet offshore 

 in 4 feet of water at the lower edge of the 

 eddy. As they encountered the edges of 

 the slack and reverse currents of the eddy, 

 the fish, rather than to follow this route, 

 pushed out into faster water to get around 

 the small point. 



It was here at the lower end of the eddy, 

 where the migration path was at its 

 narrowest and closest to shore, that the 

 electrodes were installed for Site No. 2. 



The electrodes at the second site con- 

 sisted of wire fencing material, 3 feet 

 wide, fabricated of lO-gauge wire in 2- 

 by 3 -inch meshes. The positive electrode 

 was of two layers of this wire, about 8 

 feet long, placed inshore with its inner 

 edge in about 3 feet of water, while the 

 negative electrode was of one layer, about 

 25 feet in length, placed offshore parallel 

 to the river current (fig. 2). The elec- 

 trodes were separated by a space of 

 about 5 feet, held in position on the river 

 bottom by rocks attached to the upper 

 surfaces, and were positioned so that the 

 undisturbed schools of fishpassedbetween 

 them. 



The operator had a good view of the 

 approaching and passing fish from where 

 he was standing, about knee keep in water 

 just inshore of the positive electrode. 

 With the push-button operating switch, 

 he could turn on the electrode current at 

 the proper tinne to capture the tagged fish. 



A dip net with hoop diameter of 2 feet 

 and with a 10 -foot aluminum handle was 

 used for final capture of stunned fish. 

 The net was held in a vertical position 

 along the operator's right side with the 

 hoop uppermost. When the tagged fish was 

 pulled inshore by pulsing direct current 

 toward the positive electrode, the net 

 was lowered into the water to retrieve the 

 fish, which was immobilized at the posi- 

 tive electrode about 6 to 8 feet from the 

 operator. The pulsed direct current dur- 

 ing this time was turned on and off for the 

 optimum control of the fish by use of the 

 push-buttom switch held in the left hand 

 along with the dip-net handle. 



RESULTS 



The results of electrofishing for the 

 capture of specific marked salmon at 

 Site No. 1 were only marginally success- 

 ful. The depth of the water hindered the 



