EFFORTS TO IMPROVE UPSTREAM fish migration are taking new forms around the world. In the US, Finland-based Fishheart Ltd. is piloting a hydraulic fishway system at a Connecticut hydropower plant to support the recovery of migratory species like American Shad and river herring. In China, researchers have tested a prototype tubular fishway that uses a siphon-based design to help native fish pass low dams. Meanwhile in Europe, eel tiles made from durable polymers are showing promise as a solution for helping eels and potentially other species navigate high-velocity channels. Each of these approaches aim to improve fish passage while reducing infrastructure costs and environmental disruption.
Finland based Fishheart Ltd. has launched a three-year project at the Tunnel Hydropower Plant owned by FirstLight Power in Preston, Connecticut, marking Fishheart Ltd.’s first large-scale installation site in North America.
The project follows spring 2024 tests conducted at the Santee Cooper Hydroelectric Project on the Santee River in South Carolina. Both projects are for the benefit of migratory fish species with state and federal restoration goals, including American Shad and river herring. For the first two to three years, the system will be installed at the Tunnel Hydropower Plant. If successful, it is intended to be relocated to the Stevenson Hydropower Plant in Monroe, Connecticut as a permanent fish passage solution there.
The objective of the project at the Tunnel Hydropower Plant is to demonstrate the system’s ability to attract and safely guide targeted fish species past the power plant. The Fishheart fishway is a hydraulic fish passage system that includes a floating fishway unit below the dam and a pipeline running over the dam. By requiring less permanent infrastructure construction, it is intended to be a more cost effective and adaptable system than traditional fishways. The fishway operates based on the siphon principle, guiding fish to swim into the system using attraction water flowing from upstream. Fishheart Fishways has been successfully operating at four river sites in Finland for several years. In addition to the Tunnel Hydropower Plant project, the company is currently running a test project in Menindee, Australia.
The project will serve as an important demonstration for fish management authorities, including NOAA’s National Marine Fisheries Service, the US.Fish and Wildlife Service (FWS), and Connecticut’s Department of Energy and 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
This article first appeared in International Water Power magazine.
