Assessment of the occurrence of microorganisms and other fish parasites in the freshwater aquaculture of Ukraine in relation to the ambient temperature

Background. The climate changes observed in the world over the past several decades strongly affect global aquaculture and fisheries. Ukraine is among the 24 countries, whose aquaculture and inland fisheries are currently facing medium stress, and will be potentially under higher stress in the future. The purpose of our work was to find a relation between air temperature and its impact on the spreading of infectious in freshwater aquaculture of Ukraine in the context of global climate change. Materials and methods. During 2011–2017, an epizootiological survey on experimental fishery farms of different patterns of ownership was conducted. The objects of research were the clinically healthy and diseased freshwater fish of different age groups, as well as parasites and bacteria of different etiological groups that affect aquatic organisms. A review of the clinical and parasitological study of different age groups and hybrids of silver carp, Hypophthalmichthys molitrix (Valenciennes, 1844) and bighead carp, Hypophthalmichthys nobilis (Richardson, 1845), common carp, Cyprinus carpio Linnaeus, 1758, and some cultured rainbow trout, Oncorhynchus mykiss (Walbaum, 1792), and brown trout, Salmo trutta were conducted. Research methods common for ichthyopathology, microbiology, and fisheries were used. Results. The study on fish diseases was conducted both in aquaculture and natural waters, in particular in the reservoirs of the Dnieper Cascade. Not only the growth and development of fish but also the signs and the course of various diseases appeared to depend on water temperature. The resistance of the fish and other hydrobionts to the influence of threshold temperatures depends on their adaptation to particular factors. In the years with a relatively warm vegetation period, the infection rates significantly increased to 25% and above. A significant broadening of the spectrum of parasitic infections over the last decade has been noted. An ecological misbalance in the ecosystems, an increase in the level of organic pollution of water, and, as a result, in the number of pathogenic microorganisms that may be harmful to fish and human health were registered. Conclusion. Taking into account the results of the analytical studies regarding climate change in Ukraine, we can predict outbreaks of bacterial and parasitic diseases in fish in the years to come, which may cause significant economic damage to aquaculture farms.