7792 - Laserfiche WebLink

Home Browse Search

In-water Electrical Measurements for Evaluating Electrofishing Systems by A. Lawrence Kolz U.S. Department of Agriculture Denver Wildlife Research Center Animal and Plant Health Inspection Service Denver Federal Center, Building 16 Denver, Colorado 80225 Abstract. The design of electrodes for electrofishing equipment is developed using .in-water electrical measurements that apply to any electrode configuration, and the measurement techniques require only common, inexpensive electrical meters that are readily available to field biologists. Circuit analysis techniques are described for determining the voltage, current, and power requirements for an electrofishing system, and the relation between water conductivity and electrode resistance is demonstrated. Electrode resistance values, voltage profiles, voltage gradient profiles, and comparative indices are presented for 18 common electrodes. The fallacy of monitoring voltage, current, or power as a standardization procedure for electrofishing equipment is discussed in detail. Key words: Anode, cathode, electrical shock, electricity, electrode, electrofishing, fish, voltage gradient. Electrofishing systems, designed for the capture or control of fish, induce electrical power into the water with submerged metal electrodes. These electrodes function as metal-to-water transducers and provide the interface between the power sup- ply and the water. At least two electrodes are necessary to complete an electrical circuit through water, but electrofishing systems are often electri- fied with multiple electrodes (Novotny and Priegel 1974). These arrays of electrodes provide addi- tional contacts with the water and alter the size and power density of the resultant electric field. Electrode arrays usually increase a system's area of coverage and enhance operating efficiency. Field personnel should be capable of modifying their electrodes to optimize the performance of their electrofishing equipment for the prevailing condi- tions and to compare the operating characteristics. I present technical information, measurement techniques, and comparative data to assist in the design of these electrodes. Within the past decade, fishery biologists have attempted to monitor and manage fish populations based on indices developed from electrofishing methodologies. These seasonal and time-repetitive surveys demand standardized collection methods (Heidinger et al. 1983; Wiley and Tsai 1983), which require that consistent and comparable electrical parameters be adapted for the sampling. Obvi- ously, one would not expect to seine an equal num- ber of fish with different size nets, and the same is true when electrofishing with dissimilar electric fields. Unfortunately, it is a common error to judge the electrical fields for two electrofishing appara- tus as being operationally similar based on com- parative voltage, current, or power readings at the generator or equipment control panel. The voltage and current controls actually adjust the power being applied into the water, but they do not uniquely determine the intensity of the resulting electric field. Researchers must understand that fish are electroshocked by the distribution and intensity of the electrical energy in the water (Kolz