Efficiency of a macroroughness block ramp in reducing the impact of low-head dams on riverine fish dispersion
Macroroughness ramps (e.g. with a rough bed and protruding blocks evenly distributed in staggered rows) are nature-like fishways offering a wide range of flow conditions and are expected to be very efficient tools to reduce the impact of weirs on the free movements of most life-stages of riverine fi...
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| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
EDP Sciences
2025-01-01
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| Series: | Knowledge and Management of Aquatic Ecosystems |
| Subjects: | |
| Online Access: | https://www.kmae-journal.org/articles/kmae/full_html/2025/01/kmae240112/kmae240112.html |
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| Summary: | Macroroughness ramps (e.g. with a rough bed and protruding blocks evenly distributed in staggered rows) are nature-like fishways offering a wide range of flow conditions and are expected to be very efficient tools to reduce the impact of weirs on the free movements of most life-stages of riverine fish species. However, their in situ efficiency has not been evaluated yet. Here, we used Radio Frequency Identification (RFID) telemetry to monitor during two years the displacement of eleven fish species, on such a macroroughness ramp located on a tributary of the Loire River in France. We (1) evaluated the migration rates of tagged fish species, poorly documented so far; (2) quantified macroroughness ramp attraction and efficiency; and (3) assessed the influence of fish species, fish length and environmental conditions (river discharge and temperature) on these efficiency estimates. All the species detected downstream of the weir successfully crossed the ramp, although at varying rates. Depending on the analytical approach (considering the whole study duration or taking into account different fish attempts), the ramp attraction efficiency ranged between 65.5% and 52.9%, the ramp passage efficiency between 81.8% and 77.0% and the overall efficiency between 53.6% and 41.6%. Fish between 70 and 451 mm in total length were detected crossing the ramp, usually within a short time. In comparison with the efficiency results available for other types of fishways, the macroroughness ramp studied here ranks among the most efficient devices for fish movement restoration. |
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| ISSN: | 1961-9502 |