Species composition of selected groups of parasites of the Cyprinidae fishes in water bodies of the Lviv region (2020–2026)

Purpose. To determine the characteristics of the species composition of specific groups of fish parasites in the Cyprinidae family in various types of water bodies in the Lviv region during 2020–2026 by assessing infestation levels and studying the species composition of the parasites. Methodology. The study was conducted during 2020–2026 at the Lviv Research Station of the Institute of Fisheries of the National Academy of Agrarian Sciences (NAAS) in collaboration with the Laboratory of Ichthyopathology of the Institute of Fisheries of the NAAS and the Department of Parasitology and Ichthyopathology of the S. Z. Gzhytskyi. For the ichthyopathological study, a method of complete parasitological dissection modified for fish according to K. V. Sekretaryuk (2003) was used. The species of the detected parasites were identified according to O.N. Bauer (1984). The extent of infestation (EI) was calculated as the ratio of the number of infested fish to the total number of examined individuals of the same species; it was expressed as a percentage (%); and the intensity of infestation (II) was calculated as the number of parasites of the same species per fish. Findings. The study was conducted at sampling sites and in laboratory conditions from 2020 to 2026. The study subjects were age-mixed groups of fish of the Cyprinidae family – common carp (Cyprinus carpio), crucian carp (Carassius carassius), grass carp (Ctenopharyngodon idella), silver carp (Hypophthalmichthys molitrix), and bighead carp (Hypophthalmichthys nobilis) as well as tench (Tinca tinca). During monitoring of the ichthyopathological situation in water bodies in the Lviv region throughout the study period of 2020–2026, pathogens of invasive fish diseases belonging to various taxonomic groups were identified. In particular, ectoparasitic crustaceans of the class Crustacea (Argulus sp., Lernaea sp., Sinergasilus sp.), ciliates of the type Ciliophora (Ichthyophthirius multifiliis, Trichodina epizootica), as well as helminths: monogeneans of the class Monogenoidea (Dactylogyrus sp.), trematodes of the class Trematoda (Diplostomum spathaceum, Posthodiplostomum cuticola), cestodes of the class Cestoda (Ligula intestinalis, Bothriocephalus acheilognathi, Khawia sinensis), and nematodes of the class Chromadorea (Philometroides sanguinea). Originality. Based on long-term monitoring (2020–2026), data on the species composition of pathogens causing invasive diseases and the parasite load in cyprinids of various age groups in water bodies of the Lviv region have been systematized and updated. Practical Value. The results obtained will contribute to improving epizootiological control, early diagnosis of parasitic infestations, and reducing economic losses in fish farming. They also provide a scientific basis for developing preventive and antiparasitic measures, optimizing fish farming technologies, and improving biosecurity in aquaculture.