SEIDEL and KLIMA: CRITERIA FOR ELECTRICAL HARVESTING 



Figure 4. — Percent positive response of Spanish sardines to 

 various combinations of voltage, pulse rate, and pulse width. 



PUISE WIDTH MS 



IS 3S 3S 



S 3S 35 



PUISE RATE 



Figure 5. — Percent positive response of round scad to various 

 combinations of voltage, pulse rate, and pulse width. 



Table 1. ^Percent of thread herring and bumpers at various 

 stimulation parameters. Each observation consisted of 15 

 individuals except where noted. 



'7 individuals. 

 ^31 individuals. 



pulses/s. Based on the limited data for thread 

 herring and bumper, the best pulse rates were 

 25 to 35 pulses/s. 



A factorial analysis was used to determine the 

 most effective combination of pulse rate, width, 

 and voltage for controlling Spanish sardines, 

 scaled sardines, and round scad (Table 2). This 

 analysis demonstrates that selection of the proper 

 level of voltage, pulse width, and pulse rate are 

 clearly important for controlling these species. 



Another important aspect may be the interactions 

 between the three main effects, although the 

 meaning behind this significance is uncertain. It 

 can be seen from Table 2 that these interactions 

 vary between species. Interdependence was 

 observed for all tested electrical combinations in 

 scaled sardines and Spanish sardines. Surpris- 

 ingly, this was not observed for the round scad. 

 Voltage and pulse rate interact for scaled sardines 

 and round scad. 



General observations for the first (captured) 

 group of fish indicated if the electrical combina- 

 tion was not adequate, these fish would immedi- 

 ately escape to the side or towards the cathode. 

 However, at times when the pulse width was 0.3 

 ms, thread herring would elicit a jump and skip on 

 the surface of the water and dart out of the field. 

 This escape behavior was never observed at the 

 wider pulse widths. Controlled fish would swim to 

 the anode and circle between the plates of the 

 electrode from the inside of the field to the back 

 of the field and back again in a circular swimming 

 motion, and were held until the power was turned 

 off. 



The most effective electrical combinations for 

 each species are listed in Table 3. We felt that 

 if 70% or more of the experimental group re- 

 sponded positively, the combination was effective. 

 Output voltages of 60 V or less were ineffective 

 for controlling fish regardless of the pulse rate or 

 pulse width. Effective fish control required an 

 output voltage of at least 90 V with a pulse rate 

 of 25 or more, and except for bumper the pulse 

 width had to be 0.8 ms. An overall effective 

 electrical combination was 120 V at 25 to 35 

 pulses/s at 0.5 to 0.8 ms, and 90 V at 25 to 35 

 pulses/s at 0.8 ms. 



Wild Fish 



The second group of fish was attracted into 

 the electrode configuration by a surface night- 

 light positioned above the electrodes and then 

 stimulated. Usually we were successful in attract- 

 ing sufficient quantities offish to evaluate a spe- 

 cific combination of electrical parameters. How- 

 ever, their exact position between the electrodes 

 was never the same, especially when a large school 

 of 30 to 50 fish were positioned between the elec- 

 trodes. We only used electrical field characteris- 

 tics which appeared to be successful during our 

 daytime experiments with individual captured 



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