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Guidance by electricity, joke or possibility?
Uwe Weibel, Ins:tut für Umweltstudien, Weibel & Ness GmbH, Ulrich Rost, EnBW Erneuerbare und Konven:onelle Erzeugung AG
Overview
• Blocking and guiding of downstream migrating salmon smolts/eels along an electric barrier in a bypass with optimal configuration
• Guidance is achieved by rows of electrodes which are angled to flow
direction • Screening of efficency by active telemetry
– Each fish is tagged with an individually coded transmitter – Detection in all possible migration routes by antennas in the water
• Spring 2015: 148 Salmon smolts
• Autumn 2016: 120 Silver eels
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Fish barrier
• Three rows of electrodes with independent electric fields
• Each electric field can be run with individual settings
• DC current, 50 – 90 Volt • Parameters:
– Impulse lenght – Distance between impulses – Number of impulses per group – Distance between groups of
impulses
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Telemetry
• Main principle – Signal from transmitter (every 1,5 s) – Detection of signal at antennas – Stronger signal closer to the antennas,
weaker signal with increased distance – Battery needed for active telemetry;
limited lifetime, but greater detection range
• Abdominal implantation of individually coded transmitters (surgical operation)
• Permit based on German Animal Protection Law granted by RP
Karlsruhe
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Detec:on sites
1. Glasersteg, approx. 200 meters upstream of the intake
3. Slightly upstream fish barrier 5. Bypass
7. Hydropower sta:on
9. Rotherma-‐Brücke, downstream Bypass in the river
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Detec:on site 1 (Glasersteg) Detec:on site 2 (Fish barrier)
Detec:on site 4 (Hydropower sta:on) Detec:on site 5 (Rotherma) 7
Abdominal implanta:on
• At first, fish are slightly anaethetised in water with low concentration of anaethetic
• Afterwards, narcosis by higher concentration of anaesthetic Realization 1. Opening of abdominal cavity 2. Insertion of transmitter in abdominal cavity 3. Fixation of antenna on one side of abdominal cavity 4. Suturung of the wound 5. Desinfection
Time for surgical implantation: approx. 5 minutes/fish
• Transmitter remains in the fish • Use of sterile instruments • Risk of infection very low
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Trials with salmon smolts
• Insertion point of the fish approx. 900 meters upstream fish barrier • 148 fish in 3 tranches:
– 21.04.2015: 44 fish – 27.04.2015: 56 fish – 28.04.2015: 48 fish
• Water temperature > 10 °C • Flow conditions upstream fish barrier 0,6 – 0,85 m/s • Constant amount of water through spillway and bypass • One gate at the intake was closed dureing the trial period (on the left
side next to the spillway)
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Results
• It was possible to retrace the migration route of 128 out of 148 salmon smolts
• 20 salmon smolts with only one or no detection • Migration time mostly few hours (fastest smolt: 0,5 h from detection
site 1 to detection site 5)
• In some cases detection only after 2-3 days (slowest salmon: 85,5 h from detection site 1 to detection site 5)
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Results Salmon smolts
123 Salmon smolts were detected at the fish barrier • 90 % used the spillway and could be detected at site 5
downstream
• 10 % passed the electric field
• 5 salmons used the weir for downstream migration