Integrating taxonomic and trait analyses to assess the impact of damming on fish communities in a northern cold region river

Dams are considered one of the most important threats to freshwater ecosystems. To date, assessments of the impact of riverine impoundments are based primarily on taxonomic approaches where little can be inferred about functional ecological change. We assessed the impact of damming in a cold region river fish community in Alberta, Canada, by integrating taxonomic and trait-based approaches over time (before, during the first 5 years, and after 5 years of dam construction), considering the longitudinal habitat and environmental change created by reservoir formation (downstream, reservoir, and upstream). Integrating both approaches was found to be informative, as alterations to taxonomic composition in fish communities provided initial clues to a functional response in a spatiotemporal context. Biomonitoring should therefore explicitly consider longitudinal spatial gradients in the design, implementation, and evaluation of management actions. Understanding the underlying environmental causes of why the combination of some traits are connected to the risk of species loss or a decline in their distribution is an important step towards the development of better conservation and mitigation strategies.