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22 BIOLOGICAL REPoRr I I
<br />are crucial in the design of electrodes. These two
<br />characteristics allow the equipment designer to
<br />1. calculate the total electrical resistance for any
<br />electrode array,
<br />2. calculate the voltage distribution among the
<br />electrodes at any operating voltage and deter-
<br />mine the individual and total electrode current,
<br />3. calculate the system's total power requirement
<br />and determine the magnitude of the power dis-
<br />sipated at each electrode,
<br />4. create graphic representations of the voltage
<br />profiles (S-curves),
<br />5. create graphic representations of the voltage
<br />gradient profiles (U-curves),
<br />6. compare the size of the in-water electric fields
<br />generated by different electrodes, and
<br />7. comprehend the significance of power density
<br />and its relation to voltage gradient and water
<br />conductivity.
<br />The success or failure of an electrofishing op-
<br />eration is often considered elusive and mystifying
<br />because the in-water electrical parameters are
<br />unknown or ignored. Unfortunately, a great deal
<br />of effort has been misdirected toward the metering
<br />of the electrical parameters at the power source.
<br />These on-board electrical measurements cannot
<br />be substituted for in-water measurements be-
<br />cause the fish only respond to the stimuli in the
<br />water. Researchers will find electrofishing under-
<br />standable only when they combine the informa-
<br />tion gathered through field observations of fish
<br />reacting to electroshock with a firm measurement
<br />basis of the in-water electrical parameters.
<br />Acknowledgments
<br />I thank B. W. Mefford and T. J. Rhone of the
<br />Hydraulic Structures Section, U.S. Bureau of Rec-
<br />lamation, for their gracious consent and patience
<br />in allowing this research to be conducted at the
<br />hydraulics facility in Denver, Colo. Recognition is
<br />due S. A. Pruess of the Colorado School of Mines
<br />at Golden, Colo., for his guidance and assistance
<br />in the development of the computer codes neces-
<br />sary to perform the numerical analysis. The tal-
<br />ents of D. K. Steffen created the computer art-
<br />work. The assistance of R. E. Johnson and F. A.
<br />Bush of the Denver Wildlife Research Center in
<br />laboratory setup and the collection of data is ap-
<br />preciated.
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