Introduction

Abstract

According to both European and German legislation, the protection of fish populations against the effects of hydraulic engineering structures, such as hydropower stations and water intakes, must be ensured through suitable measures or procedures. This primarily applies to diadromous species such as eel and salmon where alternating between the aquatic ecosystems of inland waters and the sea constitutes a mandatory requirement for preserving their populations. Migrations of potamodromous species are limited to freshwater bodies, but may also involve large distances. Therefore, these species also benefit from unobstructed propagation upstream, as well as downstream with the current.