Standard Methods for Sampling North American Freshwater Fishes

Chapter 14: Standardizing Electrofishing Power for Boat Electrofishing

L. E. (Steve) Miranda


Standardization of electrofishing can help reduce the variability of survey data and potentially reduce injury to fish. Without standardization, differences among collections can be partially attributed to disparities in electrofishing methodology, intensity of the electrical field, and size of the electrical field rather than to disparities in fish abundance, population structure, or fish community composition. Such standardization is critical when electrofishing is used to monitor temporal and spatial changes of fish assemblages in waters with diverse ambient conductivities. In a field study, standardization improved predictability of electrofishing catch rates by about 15% (Burkhardt and Gutreuter 1995). In a laboratory study, standardization of power transfer allowed scientists accurate prediction of control unit settings required to immobilize fish in a wide range of ambient conductivities (Miranda and Dolan 2003). Because electrofishing is an active capture method applied to changing microenvironments that continually distort the electric field and to multiple target species that respond differently to electric fields, complete standardization is not possible with present technology, but standardization of controllable power transferred to fish is advisable.

Standardizing boat electrofishing entails achieving an accepted level of collection consistency by managing various broad factors, including (1) the temporal and spatial distribution of sampling effort, (2) boat operation, (3) equipment configuration, (4) characteristics of the waveform and energized field, and (5) power transferred to fish. This chapter focuses exclusively on factor 5; factors 1–4 have been addressed in earlier chapters. Additionally, while the concepts covered in this chapter address boat electrofishing in general, the power settings discussed were developed from tests with primarily warmwater fish assemblages. Others (See Chapter 9) recommend lower power settings for assemblages consisting primarily of coldwater fishes. For reviews of basic concepts of electricity, electrofishing theory and systems, fish behavior relative to diverse waveforms, and injury matters, the reader is referred to Novotny (1990), Reynolds (1996), and Snyder (2003).