The impact of human activities on composition and distribution of caddisfly larval communities (Insecta: Trichoptera) in the Mediterranean karst river system on the eastern Adriatic coast

Permanent Mediterranean rivers are typical for the Dinaric karst region. In general, faunistic and ecology of aquatic insects of these rivers have so far been insufficiently investigated. Therefore, we present the caddisfly community structure in a highly regulated Mediterranean karst river in Croatia, having four hydroelectric power plants and three reservoirs. Caddisflies were sampled and physico-chemical water parameters were measured at nine sites along the Cetina River and at two sites on its tributary, the Ruda River. Samples were collected monthly from August 2004 to August 2005. A total of 60 069 individuals representing 49 taxa with 29 genera and 17 families were collected. According to the Redundancy Analysis (RDA), five of the ten environmental variables can significantly explain the species composition: water temperature, COD, pH, conductivity and water velocity. Of the abiotic ecological factors recorded, the combination of depth, temperature, pH, COD and dissolved oxygen showed the highest correlation with community composition patterns. At sites with the greatest anthropogenic influence the lowest diversity of caddisflies was recorded. In this research we concluded that caddisfly larvae are good indicators in assessing organic pressure and hydromorphological modifications. Knowledge of the caddisfly’s fauna and their distribution in the area of the Cetina River is important for effective and functional protection not only for the species, but also the karst habitat where caddisfly larvae live.