Evaluation of a fine-spaced angled rack with surface bypass in providing safe and timely downstream passage for salmon smolts and silver eels

Hydropower production can cause migration delay and fish mortality, impeding the safe and timely downstream migration of diadromous fish, such as Atlantic salmon (Salmo salar) and silver eels (Anguilla anguilla). To date, only a few field performance tests, especially for eels, have evaluated the ef...

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Bibliographic Details
Published in:Knowledge & Management of Aquatic Ecosystems
Main Authors: Tétard Stéphane, Courret Dominique, Tissot Laurence, Richard Sylvain, Lagarrigue Thierry, Frey Aurélien, Mataix Vincent, Mercier Olivier, Tomanova Sylvie
Format: Article in Journal/Newspaper
Language:English
Published: EDP Sciences 2023
Subjects:
salmo salar
anguilla anguilla
fish passage solution
hydropower
downstream migration
Aquaculture. Fisheries. Angling
SH1-691
Anguilla anguilla
Atlantic salmon
Salmo salar
Online Access:https://doi.org/10.1051/kmae/2023020
https://doaj.org/article/0bc6ecaf4256402a8217641675eea7db
Description
Summary:Hydropower production can cause migration delay and fish mortality, impeding the safe and timely downstream migration of diadromous fish, such as Atlantic salmon (Salmo salar) and silver eels (Anguilla anguilla). To date, only a few field performance tests, especially for eels, have evaluated the efficiency of fine-spaced angled racks associated to a surface bypass entrance to protect fish. Here, 115 salmon smolts and 65 silver eels were radio-tracked over a 2 yr period to assess passage efficiency and passage time at a hydropower intake (50 m3.s−1) retrofitted with a 20 mm rack associated to a surface bypass (2 m3.s−1). Results showed high impediment (89.6% and 96.9% for smolts and eels, respectively), and passage efficiency for the angled rack (89.1% and 93.3%), with short passage times (median, 3 and 7.5 min). However, our results highlighted a strong influence of hydrological conditions, in enhancing fish passage, especially through the bear-trap gate. We conclude that this fish passage solution, making use of existing spillways on the study site, is highly effective for both species. Special attention must, however, be paid to bar-rack design and its cleaning system to ensure fish guidance and prevent impingement or passage through the rack, especially for salmon smolts.

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