Ecological-faunistic analysis of parasites of fish larvae and fry in the lower reaches of the Dnieper

Abstract

Global climate change on our planet against the background of growing anthropogenic pollution has become one of the decisive environmental problems of our time. Hydro Ecosystems are no exception, the level of anthropogenic load on which is constantly growing. At the moment, various kinds of toxicants have become an integral factor of the external environment for aquatic organisms, including in the reservoirs of the lower Dnieper. As a result of such progressive pollution within this water area, a rather critical ichthyopathological situation has developed. This is due to the fact that the resistance of fish to the action of parasites is determined not only by their morphological and other qualitative indicators, but also by the physiological state of the fish, and also depends on the level of negative impact on the fish of critical environmental factors. In this case, the dynamic processes of development of the parasite fauna can directly influence the composition of the ichthyofauna, including its industrial part. Changes in the composition of the parzitofauna caused by climatic and ecological factors necessitate constant monitoring. This became the purpose of the research, the results of which formed the basis of the article. The main task of the research was to conduct an ecological-faunistic analysis of parasites of larvae and fry of the main commercial fish species in the lower reaches of the Dnieper, to determine the degree of development of the parasite fauna. Selection of ichthyological and ichthyopathological samples in 2018-2020 carried out in the lower reaches of the Dnieper. Epizootic and parasitological studies were carried out in accordance with the known recommendations. Of the total number of young fish surveyed, one thousand eight hundred and twenty-two were infected with parasites. The found parasites belong to nine systematic groups: simple - 28.3%; trematodes - 31.9%; monogeneans - 16.9%; cestodes - 3.0%; nematodes - 1.3%; scrapers -. 0.5%; leeches - 0.03%; crustaceans - 4.5; shellfish - 0.5. In weak-flowing areas of the water area, in juveniles of 11 species of fish we examined, we found Argulus foliaceus, metacercariae of trematodes Diplostomum spathaceum and Posthodiplostomum cuticola in 10 fish species, Ichtyophthirius polyphyphilus multiphillis and 7 species - metacercariae. In other parts of the surveyed water area, the set of parasites for certain fish species is completely different. Metacercariae Diplostom um spathaceum and Posthodiplostomum cuticola were found in larvae and fry of 9 fish species, and Bucephalus polymorphus and Myxobolus dispar in 7 fish species. Research results suggest outbreaks of bacterial and parasitic diseases in fish in the coming years, which can cause significant economic damage to the fish industry in the lowe r reaches of the Dnieper.