Modeling Fish at a National Scale: Key Features Shaping Community Structure Across Multiple Temperate Rivers

In river systems, hydrological, edaphic, structural and water quality features are known to influence fish community structure. Moreover, the presence of hydroelectric facilities regulating river flow and differences in physiographic regions may modify the relationship between community structure and environmental conditions. Although species distributions are linked to these aforementioned environmental features, their relative importance and their consistency as descriptors of community structure at a large scale has yet to be thoroughly investigated. We used survey data collected across Canada in 15 unregulated and 13 regulated rivers by a hydroelectric dam. For each river, we partitioned the variation in community structure explained by four sets of environmental features (hydrological, edaphic, structural and water quality). We then identified environmental drivers shaping community structure and compared the models among physiographic regions as well as between unregulated and regulated rivers. Our best model explained 60% of fish community. Hydrological features were predominant drivers of fish community. Physiographic region and the presence of a dam did not affect our models. Our results suggest that protocols for assessing fish community may be homogenized both in regulated and unregulated rivers establishing a common approach for biologists and hydroelectric managers across different regions.