Statistical analyses
Data analyses were conducted in R version 4.1.0 (R Core Team 2021) and R Studio 1.4.1717. For the analyses of fish community composition, we removed all fish species with an abundance ≤ 0.1% and we focused on the remaining 15 species. We used the vegan package and conducted Analysis of similarities (ANOSIM) on the Bray-Curtis dissimilarly measure (9999 permutations) to determine the significance of differences among communities of benthic invertebrates and fish upstream and downstream of the dam. We further used non-parametric Mann-Whitney U Tests to compare the total abundance of benthic invertebrates, CPUE and BPUE of fish, and condition factor of pike upstream and downstream of the dam. We used Mann-Whitney U Tests to compare the number of terrestrial insects in the gut, as well as the terrestrial index for the three most abundant fish species (i.e. roach, bleak, perch) upstream and downstream of the dam.