Comparison of Two Fish Sampling Techniques for Low‐Conductivity, Lowland Headwater Streams

Abstract

Despite being common, low-conductivity (<70 µS/cm), headwater streams are often understudied compared with larger waters that support recreational and commercial fisheries. However, recent conservation efforts that have focused on native, nongame species have created the need to develop and test sampling methods in these habitats. We compared a novel combination of gears (electrofishing coupled with kick-seining) to three-pass electrofishing for sampling fish assemblages in low-conductivity streams. At each site, each method was used to sample separate reaches equal to 35-fold the mean stream width. We compared CPUE and species richness between the two methods and used logistic regression to estimate the probability of capturing a new species on the second and third passes when electrofishing. We calculated the capture probabilities for the most common species encountered using the Carle-Strub depletion method, with the three-pass electrofishing data. When compared with the combination method, three-pass electrofishing resulted in significantly greater CPUE and species richness (0.21 vs. 0.13 fish/m 2 and 7.24 vs. 5.00 species, respectively). There was a 67% probability of capturing a new species on the second pass and 30% probability of capturing a new species on the third pass when using three-pass electrofishing. The capture probabilities ranged from 0.50 to 0.87 for the 13 species examined. The use of kick-seining after a single electrofishing pass provided no benefit compared with additional electrofishing passes. We recommend making at least three passes while electrofishing when estimating relative abundance and species richness in lowconductivity wadeable streams.Fisheries scientists are continuously investigating ways to increase sampling efficiency to best use their time and resources while collecting high-quality data that are necessary to confidently address their research objectives. Sampling effort and gear varies among projects based on the project objectives, habitats being sampled, and target species because all gear types have biases that are associated with certain habitats (e.g., riffles or pools) or groups of fish (e.g., species or size-class; Bonar et al. 2009). Because

Association of an endemic leuciscid, the Sandhills Chub, with microhabitat features and watershed‐level habitat characteristics

“…The same settings were used at all sites (DC, 600 V, 25% duty cycle, and a frequency of 60 Hz) regardless of the unit used. Despite low conductivity, pilot work and results from this study demonstrated that three‐pass electrofishing was effective at detecting Sandhills Chub (Herigan et al 2021). Sandhills Chub were detected on the first pass at 36 of the 41 sites where they were collected and were detected on the second pass at five sites, whereas they were never collected for the first time on the third pass (first‐pass capture probability = 66.4%, SD = 20.2%).…”