Fishmonitoring in the river Weser

Participants:
AOLG (Aller-Oker-Salmon-Community), des Association Leine_Salmon, the lease-community Weser 4, Ingo Brümmer of the AG(workgroup) Fischecology of the TU Braunschweig (lower-saxony) together with commercial fisherman Gernot Quaschny of the river Elbe near  Tangermuende, as well as Maik Thalmann the EON-operatioins-manager of the local hydropowerstation.

Furthermore the WSA Verden as well as the LAVES (Department of inland fisheries) were informed about this event.

Methods: In a combination of nets and electric fishing was tried to catch migrating salmonids. Within this action there was to be fished against the set out nets with the electrofishing equipement hoping the the fishes are directly caught by electricity or throughout the chase effect with nets. Shortly after doing so the nets were inspected to prevent fishes from too much damage.

Shortly before the start the sequence of action was disdussed.
 

At several places there nets set out below the hydropowerstation and than fished by the electrofishing-teams with their boats.

The team of the Fischereivereins Hannover (Verein Leinelachs) from left to right: Hans-Joachim Stünkel, Gerd Heuer and Wilfried Specht

On the picture below the third E-team of the  AGV Wolfsburg-Vorsfelde (AOLG), that consisted of Dennis Stief, Max Ludwig and Stefan Ludwig.

The team of the Anglervereins Neustadt (Verein Leinelachs) from left to right : Holger Machulla, Ingo Klein and Peter Reddert

The following net control did not bring the wished results - besides some pikeperches  and orfes no fishes could be caught by the method. Surely the the extrodinary clear water of the river Weser was a point that hindered a better catch result.

After lunch we tried in three ways to catch migrating salmonids : first by the use of a drift net, second with punctually usage of electrofishing und third in communication with the team by angling rods.

This seatrout (left picture) of about 60 cm was caught with electrofishing equipment. It had a cut-injury at its tailsegment and was set out in the upstream water of the hydropowerstation.

This nice salmon milter of  84 cm was caught by Volker Luedke with an angling rod an is held by Stefan Ludwig who planned this project.

...and Detlef Kahnert of the Leinelachs e.V. brought the fish for genetic analysis and stirping to the north-german Salmon-center in Gronau/Leine.

Following allternatives are now proofed for a further catch attempt:

1. Net-catch with a fishtrap : Gernot Quaschny and Ingo Brümmer propose the usage of a fyke-net in the bottom-water of the weir in the fish protection area.

2. Electrofishing with modified approach : In a talk to Hartwig Hahn (LSFV Schleswig-Holstein) he reported that in the river Lagan in Laholm (sweden,EON) salmon are caught like this : the hydropowerstaion is closed for the time of the fishing – thus no water runs downstream and the water level falls – after that the way downriver is closed by a net – then electric-fishing at low water-level on salmon with catodes that hang down to the ground from the boat. 

3. Fishing with angling rods. Advantage : few necessity of communication and little financial efforts. Disadvantage: stress on the animals and doubtful vitalitiy for the telemetry project as well as probably changed migration pattern after a long time of making the fish exhausted to get it into the net.

The picture shows the water level of the rivers in lowersaxony in 2007 and 2008. In those months that are mainly relevant for the spawning migration of the salmonids there was destinctively fewer water in the rivers in 2008 than it was in 2007 so that the impact of migrationsobstacles will be much higher than it was in 2007.