SEASONAL CHANGES IN INFECTION OF INTRODUCED FISH SPECIES BY INVASIVE BACTERIA IN FISH FARMS OF BELARUS

Abstract

The material for this report was the results of bacteriological examination of fish of various species (silver carp (Carassius gibelio); silver carp (Hypophthalmichthys nobilis); white cupid (Ctenopharyngodon idella); common carp (Cyprinus carpio); rainbow trout (Oncorhynchus mykiss), fry of sturgeon of Lena (Acipenser baeri) and sterlet (Acipenser ruthenus)) and various age groups in 2016–2018. in 7 fish farms in Belarus. As a result of research, 21 species of bacteria have been registered in introduced fish species in pond farms that are potential causative agents of bacterial diseases of introduced fish. Two types of bacteria – Shewanella putrefaciens and Aeromonas hydrophila – are invasive and harm the fish industry. Studies have shown seasonal changes in the frequency of occurrence of Sh. putrefaciens and A. hydrophila in introduced fish. During January-March, the infection of fish with A. hydrophila bacteria was not high, increasing sharply in April-May. In June-July, a decrease is observed, and in August is a sharp decrease in the infection of the internal organs and blood of fish with aeromonads. Bacteria Sh. putrefaciens were found in fish much less frequently than A. hydrophila, however, some seasonal dependence in the change in the frequency of its occurrence in introduced species is observed. The peak of occurrence is in June. The maximum values of the frequency of occurrence of pathogens of bacterial infections were noted for A. hydrophila in April (80.0%), for Sh. putrefaciens – in June (33.0%). It should be noted that the active consumption of mixed fodder and natural feed by the fish leads to the restoration of the body’s immune status after winter.