Quality assessment of the aquatic habitat of mountain streams in the period of minimal flow using the ichthyofauna as a bioindicator

Abstract

This paper describes the IFIM methodology (Instream Flow Incremental Methodology) for determining the minimum discharge, which, in addition to hydrological parameters, takes hydraulic, morphological and ichthyologic parameters into account as well. The basic principle of the method is the relationship between the fish population and its habitat, i.e., that most fish species prefer certain combi-nations of depths, stream velocities, and bed materials. If the values for a species living in a section of the river investigated are known, the minimum discharge for each fish species may be determined. This method was verified on reference sections of the Teplá River in the town of Sklené Teplice.