Composition of caddis larvae assemblages from altered and man-made habitats in the Drava River, Croatia

The composition of caddis larvae assemblages in altered and man-made habitats of the hydro-electric power plant system in the Drava River was studied over two years. All sampled habitats (power plant reservoirs, drainage ditches, tailrace canals and old river flow) were greatly influenced by hydro-technical management. Altogether 31 Trichoptera taxa belonging to 12 families were collected. The highest taxa richness was recorded at site in the old river flow at the first power plant. Silo nigricornis had the highest population density and dominated the communities in drainage ditches due to specific environmental conditions. The trophic relationships of the collected taxa were identified and trophic structure of larval assemblages was analysed. The assemblage structure differed among investigated habitats with passive filter-feeders – predators – grazers, piercers, grazers – detritivores or predators – passive filter-feeders as dominant feeding groups. Through multidimensional scaling (MDS) analysis, differences in the composition of the assemblages between sampling sites and clustering of samples from particular habitat types were identified. The highest clustering of samples was observed for the sites in drainage ditches and the lowest in old river flow.