Summary
The relationship between communities of chub endoparasites (Leuciscus cephalus) fished in the Orta and Pescara Rivers in the Abruzzo region of Italy, and the quality of the water in which they are caught, were studied in surveys designed to evaluate the feed quality of fish in the inland waters of the Abruzzo. Samples were taken monthly from October 2000 to September 2001 in the Orta River (Buscesi District) and the Pescara River (near the Villareia bridge); a total of 86 chub were caught. During periods of low and moderate flow in both rivers, benthonic macroinvertebrates were sampled at the fish sampling sites to classify the water quality using the extended biotic index (EBI) method. The Orta River was moderately polluted and the Pescara River slightly more polluted than the Orta. A parasitological study of the fish was conducted using conventional methods. A morphological study of the parasites led to the identification of seven species of endoparasites. Five of these (Allocreadium isoporum, Caryophyllaeus brachycollis, Caryophyllaeides fennica, Rhabdocona denudata and Pomphorhyncus laevis) were found at both sampling sites, while Acanthocephalus clavula was found only in the Pescara River and Neoechinorhynchus rutili was found only in the Orta River.

The differences in epizootological indexes (prevalence, abundance and mean intensity) and the biotic indexes (Margalef, Shannon, Evenness, Simpson and Berger-Parker) suggested that the structure of the communities of chub endoparasites in the two rivers is a less sensitive biological indicator than benthic macroinvertebrates, because it does not detect small variations in water contamination.

Keywords
Benthic macroinvertebrates, Bioindicators, Chub, Fish, Italy, Leuciscus cephalus, Parasites, Pollution.