Author(s): David Nijssen; Torsten Ode; Damien Sonny; Daniel Schmidt; Nicole Scheifhacken; Matthias Scholten; Cornelia Schutz

Linked Author(s): Cornelia Schütz

Keywords: Multispecies fishway evaluation; Electrofishing bias; Radiotelemetry; Tailwater fish assemblages

Abstract: Multispecies fishway evaluation is often based on species, sizes and abundances of fish in the fishway compared to the tailwater. One of the most established methods to evaluate fish communities in a river is electrofishing. As such, electrofishing is expected to deliver reliable data of both adult and juvenile abundances for all species in the tailwater. We have tested the comprehensiveness of electrofishing data by comparing juvenile and adult fish abundances for five of the most common species that have ascended the fishway with data from tailwater electrofishing. Using data from a simultaneous radiotelemetry experiment, we were also able to include fishway efficiency into the evaluation. Electrofishing along the river banks of a small river is shown for most species to have missed hundreds to thousands of approaches of adult Ide, Bream, Perch and White Bream, showing that restricting electrofishing deployment to daylight hours can severely reduce the detected amount of adult species and abundances. Likewise, limiting electrofishing surveys to the main spawning season will fail to detect juvenile migrations in summer and autumn.

DOI: https://doi.org/10.64697/iahr.proc.ise2026.abs.193

Year: 2026