Species richness and functional structure of fish assemblages 1 in three freshwater habitats: effects of environmental 2 factors and management 3

Anthropogenic actions can facilitate the top-heaviness of trophic levels through the introduction of novel consumers. In this present study, the inverted trophic hypothesis was 21 tested in the freshwater fish comunities of reservoir. The distribution of fish species in three 22 freshwater habitats in the Jurumirim Reservoir, Brazil, was examined using both species 23 richness and the relative proportions of different trophic groups. These groups were used as a 24 proxy for functional structure in an attempt to test the ability of these measures to assess fish 25 diversity. Assemblage structures were first described using non-metric multidimensional 26 scaling (NMDS). The influence of environmental conditions for multiple fish assemblage 27 response variables (richness, total abundance and abundance per trophic group) was tested 28 using Generalized Linear Mixed Models (GLMMs). The metric typically employed to 29 describe diversity, i.e., species richness, was not related to environmental conditions. 30 However, absolute species abundance was relatively well explained with up to 54% of the 31 variation in the observed data accounted for. Differences in the dominance of trophic groups 32 were most apparent in response to the presence of introduced fish species: the iliophagous 33 and piscivorous trophic groups were positively associated, while detritivores and herbivores 34 were negatively associated, with the alien species. This suggests that monitoring functional 35 diversity might be more valuable than species diversity for assessing effects of disturbances 36 and managements policies on the fish community.