The results of bacteriological examination were shown in the study, an examination that was conducted in the Experimental (Fish) Stocking Site, called ”Dgał” in Pieczarki near Giżycko (objects A and B) and in the Marine Biological Station of the University of Gdańsk on Hel (object C). Water and mucus from the skin surface of fish during intensive tank culture were examined. The results of water examination showed the most frequent occurrence of the bacteria TVC 22ºC, TVC 37ºC, TC, proteolytic, ammonifying and phase I nitrifying in the sea water of object C (site I). At the same time the highest count of FC bacteria was found in the tank water of object C (site II), and FS bacteria in the tank water of object B. The lowest count of TVC 22ºC, TVC 37ºC, TC, ammonifying and phase I nitrifying were marked in the tank water of object A, TC bacteria in the tank water of object C (site II), FC in the tank water of objects A and B, whereas FS bacteria in the tank water of object A and in the sea water of object C (site II). The examination of fish showed the highest occurrence of the average number of TVC 22ºC bacteria in the mucus from skin (1 cm²) of sterlet, which was taken from object A, TVCº37 C in the mucus of Russian sturgeon and starlet from the same object. The lowest average number of these bacteria was found in the mucus of bester SBS from object B. In the majority of the examined samples the occurrence of the following bacteria was found: of the genus Aeromonas, the genus Pseudomonas, the genus Flavobacterium, as well as of the Enterobacteiaceae family.

317-328