Comparison of boat electrofishing and electrified dozer trawl in the upper Mississippi and Ohio rivers

Objective The electrified dozer trawl (DT) is a novel sampling gear developed primarily to increase catch rates of invasive Silver Carp Hypophthalmichthys molitrix. Despite the growing interest in using DT as a fishery-independent survey gear, it has been primarily employed to collect Silver Carp demographic data. Knowledge gaps remain regarding its efficacy compared with boat electrofishing (EF) for sampling the broader fish community. The objective of this study was to compare two different fishery-independent sampling gears, EF and DT, to assess their effectiveness at sampling the overall fish community within navigation pools of the upper Mississippi and Ohio rivers. Methods Electrofishing samples (N = 257) and DT samples (N = 255) were collected during August–October, 2021–2022. For the most common species, differences in catch per unit effort (fish per hour) between the two gears were evaluated using generalized linear mixed models. To assess species overlap and compare community structure between EF and DT data, we estimated the Sorensen similarity index as a measure of species overlap, along with three commonly used biodiversity indices—species richness, Shannon (diversity) index, and Simpson (evenness) index—by gear at each location. Results We found that DT was more effective for capturing invasive Silver Carp and certain pelagic species. However, EF was more effective than DT for capturing most observed species. Across our sampling locations, we found moderate to low levels of species overlap between EF and DT catches, with EF catch exhibiting greater species richness, diversity, and evenness. Conclusions Our study provides managers with important information about the trade-offs between two different fisheries sampling gears. These findings underscore the importance of a gear-specific approach in monitoring, ensuring that the selected tools align with the objectives of fisheries management and provide a comprehensive understanding of both invasive species dynamics and native fish community health.