Peculiarities of the existence of a focus cyatocephalosis among wild and cultivated salmon fishes in the reservoirs of the Izhora upland of the Leningrad region

Abstract

One of the conditions for maintaining fish health in aquaculture is to control and prevent the presence of disease agents in the water supply sources of fish farms. The main advantages of industrial aquaculture to prevent the spread of parasites can be considered the use of groundwater and pellet feed. The use of an underground water source completely eliminates the possibility of the spread of parasites. In the case of using river, lakes or pounds water the consumption of pellets feed by fish should exclude their eating of invertebrates — intermediate hosts of parasites with a complex life cycle. However, we have found singles Cyathocephalus truncatus (Pallas, 1781) cestodes in juvenile rainbow trout in industrial conditions. This served as the basis for research on the spread of this parasite both in natural reservoirs and fish farms of various types located within the Izhora upland. Cyathocephalus truncatus cestode is a dangerous parasite with a complex life cycle that is widespread mainly in salmon fish. The paper presents experimental data highlighting the impact of fish farming factors and nutritional selectivity on the spread of the parasite. Special attention was paid to the infestation of Salvelinus lepecheni grown in the FSGCR in order to replenish the natural population. As a result of our research conducted over three years, fish of this species have not been invaded by the parasite in both industrial and experimental conditions. This indicates the safety of juveniles reproduced in the FSGCR for settlement in natural reservoirs. In order to determine the boundaries of the natural focus of cyatocephalosis, 106 specimens of salmon fish from 8 reservoirs were tested for infection. Methods of preventing disease in flowing pools are proposed. It has been suggested that the preservation of the focus is ensured by the progenis of the cestode procercoids, excluding the need for a definitive host (fish) to maintain the helminth population in isolated hydraulic water sources.