Fish 'passability' in modified vortex rock weir systems

Session: Poster Session

Josie Mielhausen, University of Guelph, [email protected]
Jackie Cockburn, Dept. of Geography, Environment & Geomatics, University of Guelph, [email protected]
Paul Villard, GEO Morphix , [email protected]
Andre-Marcel Baril, GEO Morphix Ltd., [email protected]

Abstract

Urbanization is a threat to river systems and associated ecosystems, specifically as flow mechanics and sediment dynamics in river systems are altered. To maintain fluvial geomorphological connectivity and aquatic ecological connectivity (i.e., fish passage) in ecosystems influenced by urbanization, watercourse alteration and modification is required. Vortex rock weir (VRW) structures are used in watercourse modification to provide both physical channel stability and habitat enhancement, including connectivity. Further, VRWs facilitate fish passage – a common goal in restoring channels impacted by urban sprawl. Field assessments were conducted at a newly constructed VRW system in Weslie Creek (Aurora, Ontario) to understand fish ‘passability’ through summer 2018. Channel geometry and velocity measurements along a sequence of 10 VRWs and 11 adjacent pool features were compared to the swimming capacity of local fish species, and percent passability was identified on cross-section and reach scales. Combined with preferred fish habitat conditions (water temperature and depth observations), passability was given a score. The major contributions from this research will inform watercourse restoration initiatives by identifying challenges and limitations to in-stream structures, suggesting best practices for design and monitoring, and influencing fish population management strategies.