[Parasites of fish in the Chiascio river].

An investigation was carried out to identify the fish parasites in the Chiascio River (Umbria, Italy). Certain physical-chemical factors and the biochemical oxygen demand of the river water were, also, studied in samples taken seasonally. The parasites found, together with the fish species they invested and the organs and apparatuses involved, are listed. The species of parasites observed are, in various degrees, diffused in the Palaearctic region. Some are considered to be of allochthonous origin. The fish species with the highest parasite infestation were, in descending order, Rutilus rubilio, Cyprinus carpio, Leuciscus cephalus cabeda and Barbus plebejus. The organs and apparatuses most frequently involved were the gills, the intestines and the skin.