Search

Regulated waterways, interconnected by navigation barriers (locks and dams), are uniquely difficult to manage, given interest in enabling native species connectivity while minimizing invasions. Canada's historic Rideau Canal Waterway, a 202 km navigable route located in eastern Ontario and connected by 24 lockstations, embodies this challenge. The lock(s) and water-control dam that compose each lockstation may respectively offer a connectivity pathway, though to what extent is unclear. We used acoustic telemetry (native largemouth bass (Micropterus nigricans) and northern pike (Esox lucius), and invasive common carp (Cyprinus carpio); n = 224) to evaluate fish connectivity relative to lock operations and environmental data over three years (2019–2021). Thirty-five passages by 23 native fishes were recorded, with 49% of passages through locks. No common carp passages were detected; movements indicate that they favour higher flow areas downstream of dams, regions with no pathway upstream. Most passages were downstream and, of concern to obligate upstream migrators, we found that multi-flight and higher-lift locks appear impassable to upstream movements. Our results suggest that these lockstations limit, but not entirely restrict, connectivity. [ABSTRACT FROM AUTHOR]

Winter is an ecologically challenging time for freshwater fishes in temperate regions. In aquatic systems that experience annual winter water-level drawdowns, the pressures that fish already face during winter can be exacerbated. The Rideau Canal, a 202 km waterway located in eastern Ontario, Canada, is one such freshwater system that encounters these challenges. The 8.3 km "Eccolands Reach," near Ottawa, experiences a considerable annual drawdown from mid-October to mid-May of 1.79–2.13 m and is home to a self-sustaining, urban muskellunge population. Because the Eccolands Reach is relatively shallow and narrow, the drawdown may significantly reduce overwintering habitat. We used acoustic telemetry and hydraulic measurements to evaluate connectivity, critical winter habitats, and residency patterns of muskellunge (N = 23) over two drawdown seasons (2020–2021; 2021–2022) in the Eccolands Reach. Our results revealed that most muskellunge overwinter in a central portion of the reach with distinct, contiguous deeper sections and that the drawdown functionally fragments the river in several areas, eliminating connectivity to adjacent habitats, by creating shallow-water barriers and high-velocity currents in riverine constrictions. Additionally, we documented potential spring spawning movements and discuss implications of reproduction prior to system refill. Our work provides insights into connectivity and winter habitats of muskellunge in a regulated waterway. [ABSTRACT FROM AUTHOR]