During the investigations into shoreline juvenile fish communities of the lower reaches of the Nemunas River carried out in 1999, 2003 and 2006, 22 species belonging to six families were caught at ten stations. Cyprinidae was the most dominant family, constituting 67.8% of the total communities, followed by Gasterosteidae (21.4%) and Percidae (9.9%). According to the occurrence frequency, Rutilus rutilus, Alburnus alburnus and Perca fluviatilis were attributed to constant species. Other fish belonged to the groups of common, rare or accidental species. During the whole research period communities were dominated by A. alburnus, Gasterosteus aculeatus and R. rutilus, which together on average made up 62.9% of the total number of the caught fish. The relative abundance of valuable fishes (vimba, asp, pikeperch) was low. In comparison with the study period of 1975–1980, the decrease in the dominance of gudgeon (Gobio gobio) was quite obvious. Significant differences were established in fish density between May, September and October (Wilcoxon test, p < 0.05), whereas the richness of species was not of great variety (p > 0.05). Great species diversity indices (H’, J’) and mean annual density show that the ecological state of juvenile fish communities in the lower reaches of the Nemunas River is comparatively good, though they are considered moderate according to the mean values of metrics of Lithuanian Fish Index (LFI).

Keywords: fish community, shoreline, ecological guilds, frequency, species richness, diversity, density, Lithuanian Fish Index, state