Salmonid Field Protocols Handbook: Techniques for Assessing Status and Trends in Salmon and Trout

Electrofishing: Backpack and Drift Boat

Gabriel M. Temple and Todd N. Pearsons

doi: https://doi.org/10.47886/9781888569926.ch8

Electrofishing is one of the most widely used methods for sampling salmonid fishes because it is relatively inexpensive and easy to carry out in a variety of conditions and has relatively low impacts to fish and other animals. Essentially electrofishing reflects the use of electricity to stun and capture fish that come within the electrical fields produced by two electrodes. The technique has been used for a variety of objectives and has generated a rich literature. This literature includes the theory and practice of electrofishing (Taylor et al. 1957; Vibert 1963; Hartley 1980; Bohlin et al. 1989; Sharber and Black 1999), the application to abundance estimation (Vincent 1971; Peterson and Cederholm 1984; Rosenberger and Dunham 2005), species richness or community structure sampling (Simonson and Lyons 1995; Reynolds et al. 2003), and estimation of the size structure of fish populations (Thurow and Schill 1996; Vokoun et al. 2001; Bonar 2002). Despite the popularity of electrofishing as a monitoring technique, recent studies have revealed that historical electrofishing practices and commonly made assumptions should be reconsidered and in some cases abandoned (Bohlin and Sundstrom 1977; Riley and Fausch 1992; Peterson et al. 2004; Rosenberger and Dunham 2005).

This paper will help fisheries biologists maximize the utility of the data produced by applying appropriate sampling designs, good planning, and optimal electrofishing techniques. In our experience, the utility of electrofishing data is frequently limited because of insufficient planning prior to field work. We have found that the most serious errors in estimates produced using electrofishing are not caused by the technique of capturing and netting fish (e.g., electrofisher settings, movement of the anode, netting); rather, errors are more likely the result of the type of estimation technique used, the validity of the assumptions, and the representativeness of the sample sites used for extrapolation. In short, it is the sampling design and analysis phases that offer the greatest potential for error reduction.

We have outlined several questions that every practitioner should ask prior to conducting an electrofishing survey (Table 1); the answers can significantly improve the utility of the data. Setting specific quantitative objectives for what the practitioner hopes to achieve is the foundation upon which all other tasks must be built. Failure to articulate specific objectives hampers the proper allocation of resources and sometimes results in the production of data of limited use.