Unconfined fishway design, implementation, and assessment for the emerald Shiner (Notropis atherinoides) in the Upper Niagara River, New York

Abstract

An engineered seawall in need of repair along the Upper Niagara River in Buffalo, NY, was previously identified as a hydrodynamic barrier to the migration of a small but important prey fish, the emerald shiner (Notropis atherinoides), and its connection to the upstream environs of Lake Erie. This study proposed a novel unconfined fishway design to be incorporated into existing plans for rehabilitation of the seawall at Broderick Park. The proposed fishway was developed using a two-dimensional depth-averaged numerical model, it was explored by placing the target fish into a physical model, and the constructed demonstration project was assessed using field measurements and observations. The numerical model showed that modular baffles attached to the seawall reduced the nearshore flow velocities to about 0.4 to 0.6 m s−1, which was within the acceptable range of velocities for the upstream migration of the emerald shiners. The physical experiments demonstrated that most emerald shiners chose to swim toward, within, or close to the proposed fishway in the presence of higher flow velocities within the main channel region. The proposed fishway design was integrated into the seawall repair as part of a demonstration project supervised by the US Army Corps of Engineers-Buffalo District. Post-construction assessment of the installation showed that (1) the modular baffles reduced time-averaged flow velocities near the seawall and water surface, (2) while very few shiners were observed swimming along the pre-construction seawall, large numbers were observed swimming upstream within this reduced flow velocity corridor created by the baffles, and (3) the structural integrity of the installation proved to be durable and resilient to extremely harsh environmental conditions. This study explored a new approach to fishway design for the passage of relatively small fish in large rivers, and it effectively melded fishway requirements into seawall restoration in concert with the expectations of multiple stakeholders.