Abstract : The department of the Creuse is hydrologically situated in headwaters, which ecologically healthy watercourses allow us to consider as a reference point. Electrofishing is used here in a geographical way in order to chart the repartition of fish species representative of a certain water quality, covering a period of seven years and a vast space of 5600km². Over the years, populations of the least sensitive species (chub and dace) progress towards upstream waters, while the most sensitive species (minnows) regress and only subsist in the headwaters. These species are indicators of a degradation of physicochemical or sedimentary conditions moving upstream.
