Assessing electric fishing sampling effort to estimate stream fish assemblage attributes

Abstract

The EU Water Framework Directive (WFD) obligates authorities to assess the ecological status of rivers. The sampling of the fish assemblage must be based on a reliable and cost‐effective monitoring programme, and it should be optimised to measure the ecological quality cost‐effectively. The efficiency of single‐pass versus three‐pass backpack electric fishing was measured to assess ecological status. The data included 295 electric fishing samplings from 137 rivers in Finland and a 5‐year data series from six small forest streams in mid‐eastern Finland. Compared with three‐pass electric fishing, single‐pass electric fishing in the same area increased the risk of missing rare fish species and species with low catchability. The concordance of the calculated fish metrics (e.g. proportion of tolerant and intolerant species) between one‐ and three‐pass measurements was, however, high, suggesting that single‐pass electric fishing was a suitable sampling procedure to evaluate ecological status. Increasing the area sampled by single‐pass removals stabilised the variances in the fish metrics and similarity indexes. It was concluded that in small streams electric fishing an area 24–27 times the stream width and in general a minimum of 300 m2, but preferably more than 450 m2, was adequate to estimate fish assemblage attributes reliably in boreal streams.

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). 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).…”

“…Boat electrofishing has been cited as a preferred method for sampling warmwater riverine habitats due to time efficiency in sampling a large area (Guy et al 2009). Long-term monitoring programs often employ single-pass electrofishing methods, sometimes in conjunction with block nets or other isolation methods (Bohlin et al 1989;Reynolds and Kolz 2012;Vehanen et al 2013), to assess changes in CPUE as an index of population size or assemblage response to natural or management-related environmental change (Temple and Pearson 2007;Reynolds and Kolz 2012). Single-pass, continuous electrofishing is a nonrepeated, constant sample effort from start to finish within a given sample event or site.…”

The effects of ecoregions and local environmental characteristics on spatial patterns in boreal riverine fish assemblages

“…(Figure 1). To ensure comparability between the sites, results only from the first electric fishing pass were used from all the sites (Vehanen, Sutela, Jounela, Huusko, & Mäki-Petäys, 2013). The average area fished was 189 m 2 (SD = 139 m 2 ).…”

Synthesis of habitat restoration impacts on young-of-the-year salmonids in boreal rivers

“…Fish data were collected in wadeable riffles following the Finnish electrofishing standard (Vehanen et al 2013). The area of an electrofishing site was typically 100-300 m 2 and data for replicate sites, if any, within a river section were pooled.…”