Study

Downstream migration of European eel at three German hydropower stations

  • Published source details Økland F., Teichert M.A.K., Havn T.B., Thorstad E.B., Heermann L., Sæther S.A., Tambets M. & Borcherding J. (2017) Downstream migration of European eel at three German hydropower stations. Norwegian Institute for Nature Research (NINA) report, 1355.

Actions

This study is summarised as evidence for the following.

Action Category

Install nature-like fishways

Action Link
Eel Conservation in Inland Habitats

Install rock-ramp fish passes

Action Link
Eel Conservation in Inland Habitats

Install pool-and-weir fish passes

Action Link
Eel Conservation in Inland Habitats

Install fish passes (type not specified)

Action Link
Eel Conservation in Inland Habitats

Modify operation of underwater turbines

Action Link
Eel Conservation in Inland Habitats

Install vertical-slot fish passes

Action Link
Eel Conservation in Inland Habitats
  1. Install nature-like fishways

    A study in 20142016 in a river near Bonn in Germany (Økland et al. 2017) found that a nature-like fishway and canoe pass at a hydropower station were used by low numbers of European silver eels Anguilla anguilla to migrate downstream. In two experiments, a nature-like fishway and canoe pass were used by 2 of 91 (2%) and 3 of 74 tagged eels (4%) that were tracked passing the power station. The remaining eels passed via a spillway gate or ice gate (3654 eels, 4959%), a surface bypass via a rack and debris flushing channel (2022 eels, 2427%) or a vertical-slot fish pass (79 eels, 812%). In 2014 and 2015, silver eels were captured in the river (134136 eels/year, 60112 cm length), fitted with radio tags, and released 10 km upstream of the power station. Stationary receivers were placed at migration routes past the power station, including a nature-like fishway and adjacent canoe pass (eels using the fishway or canoe pass could not be differentiated). Tagged eels were recorded passing the power station from October 2014 to July 2015 and October 2015 to May 2016.

    (Summarised by: Anna Berthinussen)

  2. Install rock-ramp fish passes

    A study in 20152016 in a river in southern Germany (Økland et al. 2017) found that a rock-ramp fish pass at a power station was used by low numbers of European silver eels Anguilla anguilla to migrate downstream. Of 102 tagged eels that passed the power station, three eels (3%) passed through a rock-ramp fish pass. The remaining eels passed through a section containing the turbine (66 eels, 65%), over the dam or via flood gates (24 eels, 23%) or via a side stream (9 eels, 9%). In 2015, a total of 136 silver eels (65101 cm length) were captured in the river, fitted with radio tags, and released 10 km upstream of the power station. Stationary receivers were placed at migration routes past the power station, including a rock-ramp fish pass installed for upstream migrants (details not provided). Tagged eels were recorded passing the power station from October 2015 to May 2016.

    (Summarised by: Anna Berthinussen)

  3. Install pool-and-weir fish passes

    A study in 20142015 in a river in Germany (Økland et al. 2017) found that two fish passes, including a pool-and-weir fish pass, at a hydropower station were used by almost one-fifth of European silver eels Anguilla anguilla to migrate downstream. Of 111 tagged eels that passed the power station, 19 eels (17%) used a pool-and-weir fish pass, and 16 eels (14%) used another fishway (design not reported). The remaining eels passed via an ‘Archimedes’ screw turbine (45 eels, 41%), through a ‘Francis’ turbine or a debris opening at the turbine (19 eels, 17%) or over the dam (12 eels, 11%). In 2014, a total of 136 silver eels (60114 cm length) were captured in the river, fitted with radio tags, and released 4.6 km upstream of the power station. Stationary receivers were placed at migration routes past the power station, including a pool-and-weir fishway adjacent to an ‘Archimedes’ screw turbine and a fishway adjacent to a Francis turbine (details not provided). Tagged eels were recorded passing the power station from October 2014 to July 2015. 

    (Summarised by: Anna Berthinussen)

  4. Install fish passes (type not specified)

    A study in 20142015 in a river in Germany (Økland et al. 2017) found that an unspecified upstream fish pass, along with a pool-and-weir fish pass, at a hydropower station were used by less than one-fifth of European silver eels Anguilla anguilla to migrate downstream. Of 111 tagged eels that passed the power station, 16 eels (14%) used a fish pass (design not reported) and 19 eels (17%) used a pool-and-weir fish pass. The remaining eels passed via an ‘Archimedes’ screw turbine (45 eels, 41%), through a ‘Francis’ turbine or a debris opening at the turbine (19 eels, 17%) or over the dam (12 eels, 11%). In 2014, a total of 136 silver eels (60114 cm length) were captured in the river, fitted with radio tags, and released 4.6 km upstream of the power station. Stationary receivers were placed at migration routes past the power station, including a pool-and-weir fish pass adjacent to an ‘Archimedes’ screw turbine and an unspecified upstream fish pass adjacent to a Francis turbine (details not provided). Tagged eels were recorded passing the power station from October 2014 to July 2015.  

    (Summarised by: Anna Berthinussen)

  5. Modify operation of underwater turbines

    A study in 20152016 in a river in southern Germany (Økland et al. 2017) found that lifting a turbine at a power station allowed more than half of migrating European silver eels Anguilla anguilla to pass safely, although a third of eels still passed through the turbine when it was lowered. Thirty-four of 66 tagged eels (52%) passed through the section containing the turbine while the turbine was lifted. Twenty-four eels (36%) passed through the turbine when it was lowered. Data on turbine operation was not available when the remaining eight eels (12%) passed the turbine. A further 36 tagged eels passed the power station via other routes (24 eels over the dam or via flood gates, nine eels via a side stream, three eels via a fishway). In 2015, a total of 136 silver eels (65101 cm length) were captured in the river Kinzig, fitted with radio tags, and released 10 km upstream of the power station. Stationary receivers were placed upstream and downstream of a movable ‘Kaplan’ bulb turbineat the power station. Tagged eels were recorded passing the power station from October 2015 to May 2016 when the turbine was lifted (on 12 occasions for an average of 2.3 days, total 35 days) and lowered (the remainder of the time). 

    (Summarised by: Anna Berthinussen)

  6. Install vertical-slot fish passes

    A study in 20142016 in a river near Bonn in Germany (Økland et al. 2017) found that a vertical-slot fish pass at a power station was used by low numbers of European silver eels Anguilla anguilla to migrate downstream. In two experiments, a vertical-slot fish pass was used by 7 of 91 (12%) and 9 of 74 tagged eels (8%) that were tracked passing the power station. The remaining eels passed via a spillway gate or ice gate (3654 eels, 4959%), a surface bypass via a rack and debris flushing channel (2022 eels, 2427%) or a natural fishway or canoe pass (23 eels, 24%). In 2014 and 2015, silver eels were captured in the river (134136 eels/year, 60112 cm length), fitted with radio tags, and released 10 km upstream of the power station. Stationary receivers were placed at migration routes past the power station, including a vertical-slot fish pass installed for upstream migrants (details not provided). Tagged eels were recorded passing the power station from October 2014 to July 2015 and October 2015 to May 2016.

    (Summarised by: Anna Berthinussen)

Output references
What Works 2021 cover

What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, mammals, forests, peatland and control of freshwater invasive species. More are in progress.

More about What Works in Conservation

Download free PDF or purchase
The Conservation Evidence Journal

The Conservation Evidence Journal

An online, free to publish in, open-access journal publishing results from research and projects that test the effectiveness of conservation actions.

Read the latest volume: Volume 22

Go to the CE Journal

Discover more on our blog

Our blog contains the latest news and updates from the Conservation Evidence team, the Conservation Evidence Journal, and our global partners in evidence-based conservation.


Who uses Conservation Evidence?

Meet some of the Evidence Champions

Endangered Landscape ProgrammeRed List Champion - Arc Kent Wildlife Trust The Rufford Foundation Mauritian Wildlife Supporting Conservation Leaders
Sustainability Dashboard National Biodiversity Network Frog Life The international journey of Conservation - Oryx Cool Farm Alliance UNEP AWFA Bat Conservation InternationalPeople trust for endangered species Vincet Wildlife Trust