SEIDEL and KLIMA: CRITERIA FOR ELECTRICAL HARVESTING 



Table 4. — Responses of wild fish attracted to electrode configuration at preselected electrical combinations (pulse width — 



0.5 millisecond). 



tory studies. The range of pulse widths was 

 slightly narrower in the field than in the labora- 

 tory where the experiment tank maintained a uni- 

 form field, test animals could not escape, and in 

 which narrow pulse widths were not possible. 

 Since wide pulse widths require more electrical 

 energy, it is desirable to select the narrowest 

 pulse width possible which will allow proper con- 

 trol of the species. This in situ investigation 

 clearly demonstrates that pulse widths between 

 0.5 and 0.8 ms can be effectively employed in open 

 water situations in conjunction with proper field 

 strengths and pulse rates. Our results demon- 

 strate that the effective control of the fishes tested 

 requires no less than 15 V/m at pulse widths of 0.5 

 ms or greater and pulse rates ranging between 

 20 and 35/s. A pulse width of 0.3 ms was com- 

 pletely ineffective within the proper field strength 

 and pulse rate range used in our experiment. - 



A review of the field test data suggests an 

 additional parameter, minimum pulse control 

 power for a specific pulse width and field strength, 

 should be determined during future field experi- 

 ments. Obviously a minimum output voltage and 

 current is necessary to maintain the established 

 15 V/m in any particular electrode configuration 

 and resulting load resistance. However, once the 

 minimum power to maintain 15 V/m is reached, if 

 future research can establish that a pulse enve- 

 lope of minimum total power within a minimum 

 and maximum set of values for pulse rate and 

 pulse width is the important criterion for proper 

 fish control, much greater latitude would be pos- 

 sible in designing a pulse generator for a par- 

 ticular fishing system. This would permit a 

 designer to better select pulse rate, pulse width, 

 and maximum values for voltage and current 



to provide better equipment reliability and pos- 

 sibly cheaper construction. 



The power required to control fish is presented 

 in the following discussion based on the param- 

 eters of pulse width, pulse rate, and field strength 

 which we used as criteria during the field tests. 

 Power for each pulse {Pp ) is described as: 



Pp ^Ve Xl X P^, (1) 



where Ve = electrode voltage 



/ = current at load resistance in 



amperes 

 P„, = pulse width, milliseconds. 



The total load resistance equaled 0.05 ohm with 

 an electrode-to-electrode resistance of 0.033 ohm 

 and a cable loss of 0.017 ohm. Slight daily 

 variations of 0.006 ohm were noted in electrode- 

 to-electrode resistance due to small changes in 

 salinity and temperature. For computations, we 

 rounded the resistance values slightly and the 

 electrode-to-electrode voltage was established as 

 60% of the output voltage. The current (/) and 

 electrode-to-el"ctrode voltage (Vg ) at selected 

 output voltages using an array resistance of 0.03 

 ohm and a loss resistance of 0.02 ohm were: 



Output 

 voltage 



150 



120 



90 



Ve 



90 



72 

 54 



I 



3,000 

 2,400 

 1,800 



The total power (kW) delivered into the electrode 

 array after cable losses can be computed as follows; 



663 



