Fish are good indicators for the assessment of streams because they show the interaction of various human influences on the water bodies over long periods. These include changes in structural habitat diversity or discharge regulations, the presence of longitudinal migration obstacles, or the interconnection of the water bodies with their tributaries, as well as chemical water quality and temperature conditions. Based on four meaningful parameters, a rough assessment of the fish ecological conditions in selected, representative test stretches is made.

The fish module is currently under revision

Recorded parameters:

Ichthyofauna composition and species dominance, population structure of indicator species (age classes, reproduction), population density of indicator species, deformities and anomalies


The variations in the parameters are evaluated using a points system and the relevant section of water is finally assigned to one of five different categories.

A FOEN mandated Excel-tool for a semi-automatic evaluation of the fish stock was developed in 2013.