Comparison of Single-Pass Electrofishing to Depletion Sampling for Surveying Fish Assemblages in Small Warmwater Streams

Species diversity and richness, relative abundance, and community structure were compared between simultaneous single-pass electrofishing and depletion sampling. Additionally, the number of fish displaced from sample reaches when not using block nets was estimated at each sample site. A total of 40 depletion samples was obtained during the spring and summer of 1999 and 2000 in small first- and second-order warmwater streams of central Tennessee; first passes were used as single-pass samples. Shannon-Wiener diversity values obtained with the single-pass approach were strongly correlated to those obtained with depletion sampling (r2 = 0.95). The same number of species was captured using both approaches in 15 of 40 streams; depletion sampling richness values exceeded single-pass values by more than two species in only one stream. Using bootstrap analyses, relative abundance values from single-pass samples differed from those of depletion samples in 21 of 40 streams. However, community structure comparisons using similarity indices (SIMI) indicated that the single-pass approach effectively sampled fish abundance. SIMI values were above 0.90 in 32 of 40 streams and above 0.75 in the other eight. Fish were displaced from sample reaches when not using block nets in 32 of 40 streams, but displaced fish species represented less than 10% of the total number of species in 29 of these streams. Fish movement from sampled reaches did not negatively affect estimates of diversity, richness, or relative abundance; the single-pass approach effectively sampled fish communities in these streams.