Monitoring fish communities in wadeable lowland streams: comparing the efficiency of electrofishing methods at contrasting fish assemblages

Abstract

Electrofishing is considered a reliable tool to assess the assemblages and biodiversity of fish in wadeable streams. The most widely used electrofishing techniques (point [P], single-pass [S-P], and multiple-pass [M-P]) vary as to the effort needed for sample collection, and this may potentially influence the degree of accuracy. Moreover, little is known about the comparability of the methods and their specific performance in streams with different fish assemblages. The aim of this investigation was to validate (using M-P sampling as reference) the use of P and S-P electrofishing techniques to accurately assess the richness, density and size distribution of fishes in small streams at both regional and global scale independently of fish assemblages and geographical region. We sampled 50-m-long reaches in a total of 33 lowland stream reaches that were located in different climatic and biogeographical regions (Uruguay and Denmark) and hosted different fish assemblages. Subtropical fish communities exhibited higher richness (Uy: 12-32, Dk: 1-9) and densities (Uy: 1.3-5.2, DK: 0.1-4.9 in. m(-2)) than temperate streams. We applied both "global models" using the entire database (33 sites) and "local models" including the same number of sites but using the climatic region as a model variable. Regression analyses revealed that the P, S-P and M-P methods all provided an adequate picture of the species composition and size distribution, and transfer equations for comparison between methods are thus not required. Conversely, richness was better predicted by S-P and by P techniques for regional and global models, respectively. Transfer equations obtained for abundance revealed that the P and S-P models can accurately transform catch data into M-P estimations. The transfer equations provided here may have great relevance as they allow relatively reliable comparisons to be made between data obtained by different techniques. We also show that less intensive sampling techniques may be equally useful for monitoring purposes as those requiring more intensive efforts (and costs). We encourage validation of our developed transfer equations on data from other regions of the world.

Revealing the pathways by which agricultural land‐use affects stream fish communities in South Brazilian grasslands

“…We sampled fish from 150‐m stream reaches using single‐pass electrofishing (EFKO GmbH model FEG 1500). Single‐pass electrofishing has been shown to be adequate to detect trends in fish abundance and species richness given standardised effort (Bertrand, Gido & Guy, ; Sály et al ., ; Teixeira‐de Mello et al ., ), and is cost‐effective for large geographic‐scale studies (Meador, McIntyre & Pollock, ). We sampled standardised 150‐m long reaches because previous evaluations indicated that representative samples of fish species for small streams can be obtained from reaches 30–40 times the mean wetted width or at least 150 m (Reynolds et al ., ; Sály et al ., ; David et al ., ).…”

Passability of Potamodromous Species through a Fish Lift at a Large Hydropower Plant (Touvedo, Portugal)

“…Our results showed that the mean value of this indicator was higher than 1 for the barbel, suggesting that more individuals were using the fish lift compared to those that were available downstream and captured by electrofishing. As outlined above, such results should be analyzed with caution as most barbel, particularly the larger individuals, often dwell in deep pool habitats [9] where electrofishing is clearly less effective [74], and thus their population downstream that is potentially available to migrate could have been under-evaluated. The use of other techniques, such as mark-recapture or passive integrated transponders (PIT) telemetry [75], can be useful to provide more accurate data on barbel stocks arriving at the foot of large-scale barriers.…”

Effectiveness of Continuous versus Point Electrofishing for Fish Assemblage Assessment in Shallow, Turbid Aquatic Habitats

“…MANAGEMENT BRIEF produced data of comparable precision for evaluation of CPUE trends (similar to Teixeira-de Mello et al 2014) for the more common species. The potential increase in the variety of habitats sampled during continuous electrofishing suggests that this method may better address the collection of "whole assemblage" monitoring data, similar to the conclusions of Vehanen et al (2013).…”

“…The potential increase in the variety of habitats sampled during continuous electrofishing suggests that this method may better address the collection of "whole assemblage" monitoring data, similar to the conclusions of Vehanen et al (2013). Additionally, the collection of rare taxa may be critical to monitoring programs and continuous electrofishing yielded greater species richness (similar to Teixeira-de Mello et al 2014), including seven relatively rare species that were only collected in continuous samples (versus two species collected only in point samples). The results suggest that continuous electrofishing would be particularly appropriate for collecting presence-absence data as rare species typically lead to difficulties in producing meaningful abundance analyses (Angermeier and Smogor 1995;MacKenzie et al 2005;Maxwell and Jennings 2005).…”

“…Although there have been multiple studies comparing electrofishing techniques, such as single-versus multiple-pass sampling, on a variety of streams and species (Pusey et al 1998;Edwards et al 2003;Reid et al 2008;Sály et al 2009), there have been few studies comparing continuous and point electrofishing methods (Teixeira-de Mello et al 2014). In 2009, we began a project to evaluate the relative effectiveness of point and continuous electrofishing for collecting representative data to estimate fish assemblage diversity and richness in the lower Atchafalaya River Floodway system.…”