Longitudinal pattern in fish assemblages in the upper Warta River, Poland

Abstract

The longitudinal pattern in fish assemblage was examined in the upper Warta River on the basis of site similarity where abundance of fish was expressed as a percentage of the maximum abundance observed. Four groups of assemblages were distinguished. These assemblages were significantly different in the composition of the fish reproductive groups (according to fish spawning requirements), as well as indices of species richness (S) and species diversity (H', J'). Although the longitudinal differentiation of fish assemblages related to stream order, anthropological modification of the river ecosystem, e.g. pollution and canalization of river bed, play a dominant role in shaping the specific zonation of this river.