Helminthofauna of the Caspian fish (Vimba vimba persa) of the Agrachan Bay

The parasitofauna of the fish (Vimba vimba persa (Pallas, 1814)) in Northern Agrachan was studied in the spring of 2019, 2021 and 2023. This work examines the degree of infestation of the fish by individual parasites and identifies the qualitative and quantitative composition of the fish parasitofauna. The material was collected from commercial and scientific catches. The Agrachan Bay is located in the Caspian Sea, where the sturgeon and other fish species spawn. Eight species of parasites were detected, belonging to four classes: Monogenea, Trematoda, Cestoda, and Nematoda. Changes in hydrochemical parameters, water levels in the Agrachan Bay, and the overall decline in the Caspian Sea's level have a direct impact on the parasitic fauna of fish, including the sturgeon. The water temperature in shallow waters has a significant impact, varying from freezing to overheating depending on the season, as well as the hydrological regime, which affects the quantitative and qualitative composition of hydrobionts involved in the food chain and the reproduction chain. The conducted studies have revealed changes in the number of invasive diseases in fish. It can be noted that the intensity of infestations and the extensiveness of infestations of such numerous species as Caryophyllaeus laticeps and Diplostomum spathaceum have decreased. The decrease in the infestation of fish may indicate a deterioration in the hydrological condition of the water body, as well as a decrease in the number of waterfowl, which can disrupt the development cycle of helminths. The obtained indicators of fish infection with the zoonosis pathogen A. schupakovi indicate the persistence, active functioning, and circulation of powerful natural foci of anisakidiasis.