and Grant (1954). concluded that a variety of 

 wave shapes gave satisfactory control of the 

 fish. However, they found that wave shape ex- 

 erted an influence on the speed and smoothness 

 of movement with either continuous or inter- 

 rupted half wave rectified 60-cycle alternating 

 current being the most effective and 

 "satisfactory." They also found that capacitor 

 discharge produced "satisfactory" reactions at 

 very low average current densities (0.4 to 0.8 

 milliamperes per square inch) thus representing 

 a substantial decrease in power requirements. 



It was decided to continue the experiments 

 of Morgan (1953) and Tester (1952) to determine 

 for aholehole the optimum on-fr action and mini- 

 mum power requirements for satisfactory 

 response. It was planned to use these results 

 as a basis for calculating the necessary charac- 

 teristics of an apparatus designed to produce 

 electrotaxis in tuna in a much larger tank. 



Apparatus 



The tank (12x2x2 feet) was the same as 

 that used by MorgaJi (1953) but was lined with 



fiberglass cloth impregnated with synthetic resin. 

 Fresh sea water, flowing continuously into one 

 end of the tank and out the other, was held at a 

 constant depth of 12 inches by means of a float 

 valve attached to the outlet. The temperature 

 of the water varied from 26° to 28*C. 



Electrodes made of 1/2-inch mesh, galva- 

 nized, iron hardware cloth and measuring 24 x 

 24 inches were placed vertically at each end of 

 the tank. The distance between the electrodes 

 was 10 feet. Plastic screens were inserted 12 

 inches from each electrode to prevent the fish 

 from coming into contact with the electrodes. 

 Batteries, mech^^nical interrupter, rheostat, 

 ammeter, and a reversing switch made up the 

 rest of the equipment. The schematic diagram 

 is shown in figure 1. 



Automobile storage batteries were used 

 rather than a d.c. generator in order to reduce 

 the inductance effect which causes arcing at 

 the interrupter c ontac t s and a distorted 

 wave form. Eleven batteries were neces- 

 sary to obtain the highest current densities 

 required. 



BATTERIES 



RHEOSTAT 



INTERRUPTER - 



MOTOR a 

 CAM 



A) AMMETER 



WATER 

 OUTLET 



t 



Figure 1. --Schematic diagram of apparatus used in experiments with aholehole. 



3 



