Distinction of nektonic and benthic communities between fish-present (Salvelinus fontinalis) and natural fishless lakes

Natural geographic barriers and escarpments inhibited the post-glacial colonisation of numerous lakes by fish on the eastern Canadian Boreal Shield. The aim of this study was to assess how different top-down control in lakes containing a single fish population of brook trout (Salvelinus fontinalis) and naturally fishless lakes affects the characteristics and structure of littoral macroinvertebrate communities throughout the ice-free season. Nektonic and zoobenthic communities were examined through univariate community characteristics [abundance, species density, species richness (D), evenness (J'), diversity, N')] and multivariate species assemblages. The total abundance of nektonic and zoobenthic communities and their univariate diversity indices were similar between fish-present and fishless lakes over the entire sampling period. However, species assemblages for both types of macroinvertebrate communities were significantly different between fish-present and fishless lakes throughout the season. Typically, the same invertebrate species occurred in the two lake types; but their relative abundance was different. The results of our study show that the top-down control in fish-present and fishless lakes leads to different littoral community structures, which were not perceptible through the studied univariate community characteristics. This study highlights the importance of selecting appropriate indicators for the assessment of invertebrate communities in lakes of the eastern Canadian Boreal Shield.