Study

Tests of two types of bypass for downstream migration of eels at a small hydroelectric power plant

  • Published source details Gosset C., Travade F., Durif C., Rives J. & Elie P. (2005) Tests of two types of bypass for downstream migration of eels at a small hydroelectric power plant. River Research and Applications, 21, 1095-1105.

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 1999–2002 in a river in Halsou, France (Gosset et al. 2005) reported that a bypass system located on the river bottom alongside a bar rack at a hydropower station was used by more European silver eels Anguilla anguilla for downstream migration than a bypass located at the surface. Results are not based on assessments of statistical significance. Over three years, out of 70 tagged eels, 15–19 eels (2127%) used the bottom bypass and 3–5 eels (47%) used the surface bypass, while 10–13 eels (1419%) passed through the turbines, 3–4 eels (46%) passed over the weir and one eel (1%) used a fishway. Over three years, a total of 637 eels were captured after passing through the surface and bottom bypasses. A surface bypass (flap gate; 1.4 m length, 0.9 m width) and bottom bypass (‘motorized gate’; 1.2 m length, 1.3 m width) located on the right bank of the forebay (4-m depth) were opened alternately every other day to allow passage of eels. An angled bar rack (‘trashrack’; 30 mm bar spacing, 20° from the vertical, 20 m length and 3 m height) was located adjacent to the bypasses. Between October and January in 1999–2002, a total of 70 silver eels were captured, fitted with radio tags, and released upstream of the power plant. Untagged eels were caught in a trap below the bypasses in 1999–2001. 

    (Summarised by: Sam Reynolds)

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