Examination of a Single-Unit, Multiple-Pass Electrofishing Protocol to Reliably Estimate Fish Assemblage Composition in Wadeable Streams of the Mid-Atlantic Region of the USA

Electrofishing is a valuable tool used to collect fish assemblage data, which is often vital to ecological assessments; however, wadeable electrofishing protocols vary in optimal reach length and number of passes based on study objectives, stream size, and geographic region, among other factors. This study examined a method intended to efficiently assess fish assemblage composition through the use of a single-unit, width-based electrofishing protocol using multiple passes. Fish assemblage data were collected using backpack or tote barge electrofishing equipment from 93 wadeable streams 2.3-76.4 m in width in the Susquehanna River basin (SRB). Results indicated that >97% of total species present were collected after the first two electrofishing passes, regardless of stream size. New species were more often captured on subsequent electrofishing passes in larger streams. Compared with other studies our results suggest less electrofishing effort is necessary to accurately estimate fish assemblage composition in smaller streams and in more depauperate ichthyofaunal regions. A single electrofishing pass satisfied the objective of obtaining >= 90% assemblage similarity in small streams = 5 m wide. Two electrofishing passes were necessary to reach >= 90% assemblage similarity in larger wadeable SRB streams > 5 m in width. Results suggest a single electrofishing unit and a crew of = 4 individuals can obtain reliable estimates of fish assemblage composition from wadeable streams of various sizes, which may be desirable when personnel or gear is limited. The shortcomings of single-unit, multiple-pass electrofishing (e.g., inability to model abundance or species richness) reinforce the need for managers and researchers to choose electrofishing protocols based on study objectives. Overall, our results suggest that the single-unit, multiple-pass protocol performed throughout a reach equal to 10 times the stream width is appropriate to reliably estimate fish assemblage composition in streams of the mid-Atlantic and northeastern regions of the United States.