Distribution of YOY-barbel Barbus barbus (L.) in the River Sieg/Germany

Abstract

Habitat preferences of larval and juvenile barbels Barhus barbus have only seldom been investigated, although the presence of sufficient suitable habitats for the young stages constitutes one of the most important factors influencing reproductive success of riverine fishes. Between June and September 1993, the abundance of the Young Of the Year barbels was estimated in the five defined shoreline habitats of the River Sieg/Germany using point electro-fishing and beach seine nets. In backwaters and embankment areas without of basalt rock protopterygional and early pterygional larvae were recorded only in June. The most important short-line habitats are bays and very shallow parts of gravel banks. Later, the juvenile barbels change to shallow habitats with increased current. From June to September, gravel banks and riffles are the most important habitats. It could be demonstrated that this change is size dependent. The more the fish grow, the stronger are the currents they prefer. YOY-barbels use their increased swimming capabilities to reach a habitat with the highest invertebrate density and so optimize their food supply. The riffles the most important habitat for YOY-barbels, are mainly of natural origin. In the River Sieg however most of these natural banks have been destroyed by river corrections which, therefore, have negatively influenced the reproductive success of the barbels.