Study

Bypass discharge, approach velocities and bar spacing: the three key-parameters to efficiently protect silver eels with inclined racks

  • Published source details Tomanova S., Tissot L., Tétard S., Richard S., Mercier O., Mataix V., Frey A., Lagarrigue T., Tedesco P.A. & Courret D. (2023) Bypass discharge, approach velocities and bar spacing: the three key-parameters to efficiently protect silver eels with inclined racks. Knowledge and Management of Aquatic Ecosystems, 15.

Actions

This study is summarised as evidence for the following.

Action Category

Install bypass systems alongside exclusion devices

Action Link
Eel Conservation in Inland Habitats
  1. Install bypass systems alongside exclusion devices

    A study in 20172019 in a river in southwestern France (Tomanova et al. 2023) reported that bypass systems alongside bar racks at four hydropower stations were used by all European eels Anguilla anguilla that approached intake channels when migrating downstream and no eels entered the turbines. At each of four sites, all tagged eels that approached the intake channels (total 5274 eels/site) passed through entrances to bypasses located in inclined bar racks. None passed through the bar racks into turbines. On average, tagged eels took 15 minutes to pass through the bypasses. Four hydropower stations along an 8-km stretch of river had inclined bar racks (20 mm bar spacing, 26° from the horizontal, surface area 71118 m2) installed across their turbine intake channels. Each bar rack contained three surface entrances (0.51 m wide) connecting to a bypass system. Wild silver eels (9698 female eels/year) were trapped in a river, radio-tagged and released 600 m upstream of the first hydropower station. Tagged eels were tracked using arrays of radio antennas at each of the four hydropower stations in winter 20172018 and 20182019. 

    (Summarised by: Anna Berthinussen)

Output references
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