FISHERY BULLETIN: VOL. 72, NO. 3 



Pt =Ve Xl ^ Pu X Pr (2) 



where Pr = pulse rate, pulses per second 



Pt = total power in kilovolt ampere. 



Using the above values, the total power for 

 effective electrical control values used was: 



Ve 



Pt 



The preceding results suggest there is a 

 minimum requirement of total power (Pi) to 

 properly control the fish which would be a 

 constant regardless of the specific combinations of 

 pulse width, pulse rate, and field strengths. Once 

 the effective field strength of 15 V/m is exceeded, 

 it appears that different minimum values of 

 pulse rate and pulse width can be obtained to 

 produce equally effective fish response. Unfor- 

 tunately, there are too few data points to support 

 this conclusion. To properly substantiate such a 

 hypothesis, we would have to determine either a 

 minimum pulse width for a constant electrode 

 voltage at each pulse rate or a minimum pulse 

 rate for a constant electrode voltage at each 

 pulse width. Without this, we cannot definitely 

 state that a parameter of total power (Pt) can 

 be used as a control specification rather than 

 various combinations of electrode voltage, pulse 

 width, and pulse rate. Many more tests would be 

 needed to substantiate the hypothesis, although 

 this approach would be advantageous from a 

 designer's standpoint. 



120-kVA Pulse Generator Design 



The primary objective in the design of our 

 pulse generator was to produce a system which, 

 based on the results of the 12-kVA pulse genera- 

 tor electrical fish control experiments, would 

 provide the capability for prototype development 

 and effective harvest of fish in several modes 

 of system operation. The output power of the 

 pulse generator and pulse control characteristics 

 were established to satisfy requirements for auto- 

 matic fish harvesting without nets (Klima, 1970), 

 electrical mid-water and bottom trawling for fish, 

 and to provide the potential for prototype develop- 



ment of possible future applications such as fish 

 barriers, electrical aquaculture cages, or other 

 such applications. 



Netless Fish Harvesting Mode 



The initial reason for our development efforts 

 in the field of electrical fishing was to eventually 

 achieve the automatic fish harvesting system. 

 Since this application imposed the most serious 

 power demands, the design specifics were estab- 

 lished around that set of conditions and results 

 of this study were used to calculate the power 

 requirements for a netless fishing system. Allow- 

 ances were made, however, for application of the 

 system to other electrical control applications. 

 One, a mid-water trawl mode, is described later 

 in the paper. 



Use of lights at night concentrate fish (Wick- 

 ham, 1971) in a volume of water which can then 

 be electrified. The minimum volume of water 

 within a light field which needs to be effectively 

 covered electrically to produce commercial quan- 

 tities of fish would be 5 m in cross section and 

 10 m in length. An equation for resistance of 

 seawater between the electrodes is: 



R = 



PL 



(3) 



where L 

 A 



P 



= distance between electrodes in 

 meters 



= surface area of the electrodes in 

 square meters 



= resistivity of seawater in ohm- 

 meters. 



According to this equation the load resistance of 

 two parallel plates is: 



R 



0.213 X 10 

 25 



= 0.0852 ohm 



where p at 30%o and 24°C = 0.213 ohm-m. 



However, this formula only describes the resis- 

 tance of the volume of water between two 

 electrodes as if the electrode array was a finite 

 conductor. In actual practice, a significant spread- 

 ing of the electrical field occurs in seawater. If the 

 size of an electrode is small in comparison to the 



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