A cascade of dams affects fish spatial distributions and functional groups of local assemblages in a subtropical river

Abstract Dams reduce the longitudinal connectivity of rivers and thereby disrupt fish migration spatial distribution species, impacts that remain poorly studied for some Neotropical from mega-diverse basins. We investigated species with different trophic movement/reproductive/size characteristics to assess how functional groups have responded a cascade dams on Uruguai River in southern Brazil. Fish abundance, biomass, composition were evaluated at eight locations along gradient. The assemblage upper stretch was mainly characterized by small medium-sized higher levels, whereas sites located furthest downstream displayed more medium large-sized including many carnivorous species. Species high fecundity, seasonal migrants, catfishes internal fertilization common river´s middle lower reaches. Detritivorous dominated areas distant dams. Overall, diversity local assemblages greater has impacted River. alteration reaches river potential consequences ecosystem processes services, such as nutrient cycling fisheries.