| Fish passage


Shiner Fish Passage ensures a critical food source for larger fish and wildlife. It directly supports the US$5.1bn Great Lakes recreational fishery and brings the region one step closer to the goal of delisting the Niagara River as a Great Lakes Area of Concern. The passage utilises a series of specially designed,


concrete-filled steel baffles mounted to the park’s seawall. These create channels of slower water that shiners can swim against. Measurements following construction confirmed water velocities have dropped below the shiners’ swimming threshold. The final phase of the fish passage was constructed from March 2025 to May 2026 under an US$11.8m contract awarded to Buffalo-based Bidco Marine Group. It spans 213m along the seawall at the south end of Freedom Park. Construction included repairs to the timber crib wall, the installation of steel plates at the waterline and the attachment of the concrete-filled metal baffles. Though small and seemingly abundant, the emerald shiner is a critical prey fish at the base of the food web in the Niagara River and Lake Erie. Its population has been threatened by hydraulic barriers. Previous studies by USACE, the University at Buffalo and SUNY Buffalo State University identified this stretch of the river as moving too fast for the fish to navigate. Buffalo District team members have already observed shiners passing through the project into upstream portions of the river in groups of hundreds. The team has also observed common terns hunting fish along the seawall – an activity never previously seen at the site.


Herring populations River herring populations are reported to be at historical


lows across their native range along the East Coast of North America due to overfishing, and habitat loss through degradation and damming. In the last 200 years, dams and other impoundments have reduced access to spawning habitat for these and other anadromous fish. To assess the theoretical coast-wide spawning


potential for river herring, Snyder et al quantified historically accessible spawning habitat (pre-dam) in coastal freshwater rivers using physical river characteristics such as width and gradient. And to assess the impact of dams on spawning habitat, a dams database was used to segment river reaches. This enabled characterisation of spawning habitat upstream and downstream of the dams. River-specific population models were then used to estimate the number of potential spawners for each species, based on habitat estimates and life history parameters. Three different scenarios were investigated: no dams, favourable dam passage, and no dam passage. The results showed that an estimated 52% of alewife and 51% of blueback herring habitat were located upstream of dams throughout the East Coast of North America. The authors claims that this results in a theoretical loss of ~880 million alewife and ~100 million blueback herring potential spawners due to dams, reducing both the ecological connection and fishery potential of these species.


Marine matters


Although habitat fragmentation is a major threat to aquatic biodiversity loss, much less attention has


been given to the connectivity of marine ecosystems than freshwater. New research contends that coastal infrastructure including tidal turbines have resulted in underappreciated impacts on the connectivity of fish movements, resulting in passage challenges at sea. As tidal turbines are placed in areas with high currents, these can hinder fish movement and result in entrainment, and monitoring this is in such unique areas can be very challenging. “Unencumbered passage of animals in the marine


realm is underappreciated and underdeveloped as a distinct research theme of marine ecology,” Lennox et al say in their study in Marine Ecology. Given the sparsity of published literature, Lennox et al say theirs is “a narrative and not a systematic review”. In some instances, the evidence base was so small the authors even had to rely on their own experience to contemplate potential impacts. With marine ecosystems being so vast, it is presumed that fishes, mammals, turtles and other creatures can simply avoid any barriers by swimming around them. However, the authors claim that the growing abundance of marine infrastructure is creating challenges to connectivity within the marine environment, which have not yet been thoroughly addressed by science or engineering, particularly from the perspective of fish passage. “It is imperative that we assess the potential connectivity issues resulting from marine infrastructure and that we generate solutions to mitigate these issues for marine organisms,” the authors add. Tidal turbines occur in restricted areas where


currents are forced through narrow channels, such as the Minas Passage in the Bay of Fundy in Canada or the flows between the Orkney Islands in Scotland. In areas such as the Minas Passage, these channels may represent the only migratory pathway between the ocean and essential reproductive or foraging habitats for a variety of marine and diadromous fish species. There may also be fish collisions which result in injuries and mortality, along with displacement or disruption of migratory routes. Indeed, electromagnetic fields emanating from the subsea cables transferring power from the generating site to stations onshore are believed to present a challenge to the many animals that use magnetic cues for navigation. The authors explain that there are opportunities


to install non-physical barriers, based on sensory capabilities (such as bubble curtains, electricity strobe lights, or carbon dioxide), at turbine sites. Such solutions would not only minimise the risk of injury or mortality but also guide organisms around infrastructure, mitigating barriers to connectivity caused by the turbines. According to the authors, much work is still needed to understand how effective such approaches can be and how species-specific some interventions are. Tidal streams can offer a free ride to animals that


wish to move while conserving energy, and species like eels may use tidal stream transport as part of their mobility strategy. And in such high flow areas periodic shutdowns during migratory seasons may be necessary. Lennox et al believe their review has identified several priority areas for research that could help forge new partnerships between biology and engineering disciplines to enhance the sustainability of marine infrastructure and the development and improvement of marine habitat.


References


Lessons learned from a staged approach to upstream fish passage at Site C, a new hydroelectric dam in northeastern British Columbia, Canada by Nicholas Burnett, Sarah Prior, Vincent Autier, Brent Mossop. BC Hydro. January 2026. DOI:10.2139/ssrn.6259579


A census of fish passage facilities at US hydropower developments across the conterminous United States. Paul G. Matson, Bryan B. Bozeman, Chris R. DeRolph, Gbadebo A. Oladosu, Debjani Singh, Diandre Richie, Jesus Morales, Jessica Pica, Bryan Sojkowski, Bjorn A.Lake, Nicholas B.Anderson, Blane Bellerud, Simon Dionson, Shannon Ames, Maryalice Fischer. Journal of Environmental Management Volume 391, September 2025, https://doi.org/10.1016/j. jenvman.2025.126623


Comparison of juvenile white sturgeon blade strike survival through a conventional and a novel hydropower turbine by Kenneth W. Zillig, Simone S. Lassar, Sterling M. Watson, Sarah E. Baird, Abraham D. Schneider, Nann A. Fangue. Journal of Ecohydraulics, 1–21. https://doi.org/10.1080/24705357. 2026.2636289


Impacts of dams on river herring populations through their native range: what’s left? Shawn Snyder, Daniel Stich and Joseph Zydlewski. Frontiers in Ecology and Evolution. 14:1716846. doi: 10.3389/ fevo.2026.1716846


Marine Fish Passage— Underappreciated Threats to Connectivity Within the Marine Environment. Robert J. Lennox, Heather D. Penney, Kim Birnie- Gauvin, Caitlin Bate2, Steven J. Cooke, Tormod Haraldstad, Saron Berhe, Charles W Bangley, Knut Wiik Vollset, Morgan L. Piczak. Marine Ecology, 2025; 46:e12859 https:// doi.org/10.1111/maec.12859


www.waterpowermagazine.com | September 2026 | 39


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