Evaluation of a Backpack Electrofishing Unit for Multiple Lake Surveys of Fish Assemblage Structure

We evaluated the effectiveness of a portable, backpack electrofishing unit, used from a small boat, for sampling fish assemblage structure in 11 lakes in the northeastern United States. Samples collected with a boat-mounted, 350-W backpack unit (EF-BP) were compared with samples taken by (1) two 5,000-W electrofishing units, (2) gill nets, (3) trap nets and minnow traps, and (4) seines. The EF-BP was more effective than the nonelectrofishing gears, capturing a mean of 79% of a lake's documented fish species pool. Gill nets, beach seines, and trap nets captured, on average, about 50% of the species; minnow traps were least efficient. With identical transect times, the EF-BP was as effective as a standard barge-mounted electrofishing unit for capturing species and numbers of individuals. At three low-conductivity lakes, the EF-BP collected fewer species and individuals than a semiportable 5,000-W unit but was more effective than any of the nonelectrofishing gears. Analysis of species accumulation curves for the EF-BP indicated that three or four 4-min electrofishing of transects were sufficient to collect a reasonably complete sample of the available species pool in lakes smaller than 20 ha; in larger lakes up to 900 ha, as many as nine transects were required to achieve a similar degree of sampling sufficiency.