Pharmaceutical contamination and biotic factors affecting parasitism in common carp ( Cyprinus carpio )

Abstract

Increasing levels of persistent pollutants in the aquatic environment are likely to have serious impacts on host–parasite relationships. In this study, common carp (Cyprinus carpio) of the same age, origin and source were randomly stocked in two pond localities, one fed by treated water from a municipal sewage treatment plant and the other fed by a non-polluted stream. Fish biometric parameters and health status were evaluated after 2 years of exposure through the determination of somatic condition indices, parasite load and concentration of pharmaceuticals. Municipal pollutants were found at both sites, although at significantly higher levels at the polluted site, with antidepressants, antibiotics, analgesics and beta-blockers dominant in each case. Owing to a higher availability of natural food, carp from the polluted locality displayed significantly better body condition than those from the control site, while parasite abundance and species richness were higher at the control site. Our results suggest that, compared with fish from control locality exhibiting diverse and abundant natural parasite fauna, fish from the polluted locality were better able to cope with parasites, due to their better condition status. Fish from this study site may have profited from municipal waste water by avoidance of high levels of parasite infections.