In interconnected freshwater systems like waterways and historic canals, ensuring connectivity across the landscape can stem biodiversity losses by enhancing migratory populations, supporting genetic diversity, and providing access to ideal critical habitats. However, these waterways are often plagued with anthropogenic river fragmentation and connectivity loss because of barriers like navigation locks and dams, and the diffusion and consequential negative effects of invasive species. Selectively managing barriers in waterways to promote the movements of native species while simultaneously minimizing invasive species dispersal – a conservation strategy known as 'selective fragmentation' – could provide a solution, but is a major challenge.

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 Located in eastern Ontario, Canada is the Rideau Canal Waterway, one such waterway that embodies this challenge. It is a 202-kilometre continuous navigable route that forms a connection between the Ottawa River, at Canada’s capital city of Ottawa, and Lake Ontario, at the city of Kingston. Although the waterway was originally constructed in the 1830s for commercial shipping and national defense, today it is primarily operated for recreation by the federal agency Parks Canada and for its international significance as a UNESCO World Heritage Site. The waterway features large and small lakes, riverine areas, and constructed channels all interconnected by 46 operating navigation locks, many of which have water-control or hydroelectric dams (collectively, 'lockstations'). Because waterways with barriers – like lockstations – have been referred to as invasion highways for aquatic species, it is vital to consider how infrastructure and operations could be refined to reduce invasive species spread. To do so, and without compromising connectivity for native species, we must first assess the extent that both native and invasive fishes move throughout the waterway and the ecological and/or hydraulic factors influencing movements. 

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With much help from peers, professors, and field assistants, I externally (FLOY tag) and internally (acoustic tag) tagged thousands of fish across the Rideau Canal Waterway, discovering several interesting findings. Our movement data suggests that lockstations reduce, but do not entirely restrict, connectivity, and that seasonal water-level drawdowns further reduce connectivity within river reaches. We found that most fish passages were in the direction of flow, a potential issue to native upstream migratory species. Notably, while we documented several native fish species crossing barriers, no invasive common carp passages were detected and only a single invasive round goby moved upstream through a lock. Results from my doctoral work add to the limited, but growing, literature base of native and invasive fish movements in waterways, providing evidence and suggestions for managers and conservation groups to develop selective fish passage strategies or take restorative actions. Given that waterways are pervasive globally, our hope is that this research informs not only the conservation and management of fish populations in the Rideau Canal Waterway, but of other waterways in Canada and beyond.

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Read about our findings in a fun magazine article here or see published articles from July 2021, January 2022, and November 2022.