Parasite diversity of <i>Cyprinus carpio</i> Linnaeus 1758 from the Danube River, Bulgaria

Abstract In 2019-2021, 20 specimens of common carp Cyprinus carpio Linnaeus 1758 were caught in three locations (biotopes) along the course of the Danube River in northwestern Bulgaria. Infection with five parasite species was detected – Nicolla skrjabini (Iwanitzky, 1928) Dollfus, 1960 (class Trematoda); Schyzocotyle acheilognathi (Yamaguti, 1934) Brabec, Waeschenbach, Scholz, Littlewood &amp; Kuchta, 2015 (class Cestoda); Acanthocephalus lucii (Müller, 1776) Lühe, 1911, Pomphorhynchus laevis (Zoega in Müller, 1776) Porta, 1908 (class Acanthocephala); Contrac а ecum sp. (larvae) (class Nematoda). Three of the found endoparasite species are pathogenic for fish – Sch. acheilognathi , P. laevis , and Contrac а ecum sp. (larvae). C. carpio is a new host record for Sch. acheilognathi and Ac. lucii in Bulgaria. The studied biotopes are new habitats for the established parasite species. The present study aims to provide new data on the diversity and the ecological indices (MI, MA, P%) of C. carpio parasites from the Bulgarian section of the Danube River.