Session A7: Migrational Behavior of PIT-Tagged Fish at Geesthacht Weir, River Elbe, Germany

Abstract: Nearby the town of Geesthacht, 35 km upstream of Hamburg, exist the only one migration barrier for fish on the German side of the Elbe. This weir was built in 1960 to regulate the tidal influence and to obtain a constant water level upstream. Since 1998 fish passage is provided by a natural-like bypass channel on the left side of the river. On August 1st 2010 Europe’s biggest fish pass, designed as a vertical double slot pass, was put into operation on the other stream side. Ever since a fully extended fish ecological long-term monitoring was established at that location. An essential part of this monitoring is the use of HDXTechnology (= Half Duplex) to assess fish migration on short and long Scale. In this context up to 10.000 specimens of anadromous and potamodromous species per annum, e. g. Atlantic salmon (Salmo salar), river lamprey (Lampetra fluviatilis), burbot (Lota lota) and ide (Leucisus idus) are individually tagged with PIT-Tags (= Passive Integrated Transponder) and released at both river banks up to 3 km downstream the tailwater of the weir. Redetection of upstream migrating tagged individuals is facilitated by frame antennas, which are positioned within the corridors of both fish passes. 7 antennas in the old and 23 in the new fish pass, observe automatically and continuously as well as time-, site- and individual-specific the migratory behaviour. Due to this complex setup at the monitoring site and an above average amount of marked individuals it is possible to get detailed and unique information about fish behavioural patterns in the tailwater of the weir and in different fish pass types as well as the period of time needed for the passage of fishways. The results that have been determined will be presented