| Fish passage
Left: The European eel
Environmental Protection (DEEP). Approval from these agencies is crucial for the Fishheart fishway to gain acceptance for permanent use in North America. For FirstLight, the long-term goal of the trial is to develop a successful, cost-effective solution for fish passage where it is required at its hydropower plants in North America. The Tunnel plant was chosen as the initial test site because it is located on a small river with the target species present. This environment provides a controlled setting for evaluating the fishway’s efficiency. The fish passage system operates for 2–3 months each year during the American Shad and river herring migration season, which occurs between April and July.
Tubular fishways Although experimental studies across Japan,
Indonesia and Iran have focused on tubular fishway designs and their effectiveness in aiding the upstream migration of fish over low-head weirs, Chinese research on this is still at an early stage. Described as being a first of its kind to develop and
test this prototype of fish passage in southwest China’ river systems, a new study has provided a foundation for future optimisation and broader implementation of tubular fishways across the region. As research in the Journal of Environmental Management explains, the design concept of novel tubular fishways is fundamentally different from that of traditional ones. Whereas traditionally engineered fishway designs for upstream passage include roughened ramps with weir structures, vertical slot passes, and baffle passes with fish moving upstream from one pool to the next, tubular designs utilise the hydraulic siphon principle to direct water from above the dam through the pipe to discharge downstream, attracting fish below the dam to enter the pipe and ascend to the upstream dam. In addition, tubular designs are typically made of
PVC pipe materials and do not require additional site construction before installation, and so construction costs are less than those of traditional designs.
Understanding how effective novel tubular fishways would be in the upstream migration of native fish in China’s river system is described as being crucial. That’s why a study was carried out by Senfen Ke et al at a low rubber dam on the Huangbai River in China. Results showed that the tubular fishway effectively facilitated fish migration through the dam with an attempt rate of 45.1% and a passage rate of 56.8% respectively. The attempt rate was significantly influenced by water temperature, water transparency, and dam spillover conditions. These findings, the authors claim, highlight the potential of the tubular fishway as a cost-effective and environmentally sustainable solution for fish passage at a low dam.
Eel tiles European eels also face problems when trying to
make their way through high velocity barriers when migrating upstream. As the water flow can be too fast for them to swim against it causes delays and can even prevent migration. However, eel tiles made from high density co-polymer are described as being an ‘emerging solution’ for this problem. Studies have assessed the tiles’ performance in
relation to eel passage, behaviour and kinematics when mounted on the bed of an open channel recirculating flume. It was found that the tiles effectively increased passage and allowed eels to rest without the need to swim back downstream, as well as reducing the amount of energy needed to travel upstream. By allowing the eels to continuously move upstream, the tiles potentially decrease predation and infection risk at resting hotspots and were described as being effective in helping eels pass upstream in an experimental flume. Overall, the research concluded the tiles have the
potential to be a suitable solution for the upstream passage of eels at high velocity barriers, and could also potentially work for other species of fish while not modifying the flow in the rest of the channel for fish species which may not require the tiles.
References
Design and initial evaluation of a novel tubular fishway for the rubber dam on the Huangbai River, a tributary of the Gezhouba Reservoir by Ke, S., Xiang, S., Kattel, G., Li, D., Tu, Z., & Shi, X. Journal of
Environmental Management, 381.
https://doi.org/10.1016/j. jenvman.2025.125301
Fish passage solution: European eel kinematics and behaviour in shear layer turbulent flows by Guglielmo Sonnino Sorisio, Catherine A.M.E. Wilson, Andy Don & Jo Cable. Ecological Engineering Volume 203, June 2024, 107254.
https://doi.org/10.1016/j. ecoleng.2024.107254
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