The efficiency of a nature-like bypass channel for pike-perch (Stizostedion lucioperca) in the Marchfeldkanalsystem

Abstract

This radio telemetry study is part of a large interdisciplinary research program on the colonisation and development of the Marchfeldkanal(MFK)-system, a man made channel. The immigration of fishes into the MFK is dependent on the effectiveness of fish bypass channels at several weirs. To investigate the efficiency of the lower most fishway we estimated the population densities along the MFK-system and below the weirs using electrofishing. In addition, the movements of 15 radio-tagged pike-perch at the fishway were observed. Although more than 57 000 fishes of 35 species passed the bypass channel, pike-perch (Stizostedion lucioperca) were under-represented in the fishway traps compared to their occurrence in the channel. The average daily movement of radio-tagged pike-perch was 108 m (range 6-333 m) and the maximum observed daily movement was 1050 m. The entrance to the bypass channel (280 m below the weir, and 100 m above the release site) was approached a number of times by 6 tagged fish, though none of them entered the bypass channel during the period of tracking. We conclude that although pike-perch migrate actively they do not utilise the bypass channel as much as most fish species of the MFK. Therefore the weir still represents a bottleneck for the immigration of pike-perch into the MFK.