A boat electrofishing crew consists of a driver and one or two persons who collect the fish with dip nets. The driver should be skilled at maneuvering the boat as effectively as possible to allow crew members the best opportunity to capture stunned fish. As with wadeable electrofishing methods, all members of the boat electrofishing crew must wear polarized sunglasses.
Sampling begins at the upstream boundary of the sampling reach proceeding in a downstream direction by maneuvering the boat along one shoreline. The shoreline sampled during the first pass is decided at random. The boat is operated at a speed equal to or slightly greater than the water velocity. Sampling is conducted in a downstream direction because fish are usually oriented into the direction of the flow and therefore either swim into the approaching electrical field or turn to escape downstream. Turning to escape orients the fish perpendicular to the electrical field, exposing a greater surface area of the fish to the electrical field and thus making the fish more susceptible to the electrical field. Also, when fish are stunned they are carried downstream by the flow, providing greater opportunity for capture. Thus, when sampling with an electrofishing boat, sampling in a downstream direction is more efficient than sampling in an upstream direction (Ohio Environmental Protection Agency, 1987).
Habitat features along the shoreline are sampled by maneuvering the boat close to the habitat feature with the electrical current off. As the anode array is placed near the habitat feature, the electrical field is generated and the boat is backed away from the habitat feature. The fish are thus "pulled" away from the habitat feature to facilitate their capture. All captured fish are placed in a live well on the boat and processed after completion of the first pass. A second pass is conducted along the shoreline not sampled during the first pass.
Most electrofishing operations are conducted during normal daytime working hours. However, night electrofishing studies have shown that night sampling, particularly in nonwadeable waters, can yield more species and greater numbers of individuals than day sampling (Loeb, 1957; Paragamian, 1989). This is due to a variety of factors including reduced gear avoidance at night and diurnal movements of fish. Night electrofishing of nonwadeable streams has been suggested to provide a more representative sample of fish community structure, and therefore has been recommended for long-term monitoring programs that include large rivers (Sanders, 1992). Night sampling, however, requires overtime, can produce undue fatigue and additional safety risks, and should be avoided if satisfactory results can be obtained during day sampling. Analysis of retrospective information and consultation with other fish ecologists can provide information to assist in determining if day sampling of nonwadeable streams produces a representative sample of the fish community.
Although safety is a critical concern for all sampling procedures, it is particularly so when electrofishing. Any electrical equipment can be potentially hazardous to the operator if used improperly. A survey conducted by Lazauski and Malvestuto (1990 ) noted that more than 450 reported incidents of minor electrical shocks as a result of electrofishing occurred in