ABSTRACT

Many species of fish in running waters also colonize stagnant waters and are sedentary. The ability of a species to sustain itself in running water and resist being swept away depends primarily on its swimming speed. Swimming speed varies greatly from one species to another and determines the minimum speed at which it can survive in the current. The varying swimming speed limit of different fish species results in an upstream-downstream succession of these species on a longitudinal profile of the river, as a function of the slope. The zonation of fish, as a function of the slope and width of the water course, reflects the swimming capacity of the species and the temperature. The distribution of European fish has been modified since the end of the 19th century by human intervention, including construction of canals linking the large river basins and introduction of species from one basin to another or from one continent to another.