Relationship between submerged aquatic vegetation, turbidity, and fish distribution in a large shallow fluvial lake

Many freshwater ecosystems worldwide are threatened by increasing water turbidity and extensive submerged aquatic vegetation (SAV) loss, with potential consequences on aquatic communities. Such changes in water quality and habitat features affect the relative abundance of species in the community and/or the composition of ecological guilds altering the trophic network. Here, we estimated the relationship between fish species and both SAV abundance and water quality in Lake St. Pierre (Québec, Canada), a shallow fluvial lake of the St. Lawrence River. To explain the association between the fish community and environmental variables, we performed multiple linear regressions on fish abundance, species richness, and Shannon diversity calculated at 133 stations, along a gradient of turbidity, temperature, and SAV abundance. In addition, we estimated the relationship between dominant fish species abundance and environmental variables by using canonical correspondence analysis (CCA). Species richness and abundance were positively related to SAV. Turbidity was negatively related to fish abundance, but had an unexpected positive effect on diversity (Shannon and species richness). By quantifying the association between fish species and habitat features, this study contributes to a better understanding of mechanisms structuring fish communities in changing environments.