Standard Methods for Sampling North American Freshwater Fishes, second edition

Chapter 18: Standardizing Electrofishing Power

L. E. (Steve) Miranda, James B. Reynolds, Jan C. Dean, Chad R. Dolan, and Joseph D. Buckwalter

doi: https://doi.org/10.47886/9781934874769.ch18

Electrofishing is a popular active-capture method for monitoring fish populations and assemblages in inland waters. As a monitoring tool, it has the capacity to yield large samples of target fishes over a variety of aquatic environments with a minimal workforce and with portable equipment that requires modest maintenance. Additionally, although many species and sizes of fish are susceptible to electrofishing, only target specimens may be retrieved and handled, allowing much of the catch to be released unharmed. The application of electrofishing equipment has great flexibility due to user adjustability of a system of electrodes, the output voltage, and the frequency, duration, and waveform shape of the power pulse.

Yet, the flexibility of electrofishing allows for inconsistencies in operation and application. Thus, a major concern is the standardization of electrofishing equipment, procedures, and application to ensure that data are collected consistently over time and space. Without standardization, disparities among collections are likely to be attributed to unknown levels of collection efficiency rather than dissimilarities in fish assemblages. Standardization of electric power to safe levels can also lessen injury to fish (Snyder 2003; Dolan and Miranda 2004) by constraining settings to levels likely to produce immobilization but unlikely to harm fish. However, full standardization of electrofishing is not possible because, as an active-capture method, electrofishing is applied to changing microhabitats that continually distort the electric field to affect capture efficiency (Snyder 2003; Miranda and Kratochvil 2008; Reynolds and Kolz 2012) of fish species and sizes that respond differently to electric fields (Dolan and Miranda 2003).

Nevertheless, standardization of controllable variables is advisable. Standardization entails achieving an accepted level of collection consistency by managing various broad elements, including (1) the temporal and spatial distribution of sampling effort, (2) electrofisher operation, (3) equipment configuration, (4) characteristics of the waveform and energized field, and (5) peak power transferred to fish. This chapter focuses exclusively on element 5; factors 1-4 are addressed in other chapters and in Appendix A.