Changes in bacterial quality and its relationship with some environmental parameters around the fish cage culture in the southern of Caspian Sea (Nowshahr region)

The aim of this study was to investigate the changes in the bacterial quality trend (indicator bacteria) of water and its relationship with some environmental parameters around fish cages culture in the southern Caspian Sea region (Nowshahr-Mazandaran province). For this purpose, water sampling of the southern region of the Caspian Sea in the Tuskatok region of Nowshahr city in Mazandaran province took from January 2017 to December 2016 during the rainbow trout cage culture period at different distances cage (cage shade, 200 and 1000 m).The results showed that in the whole cage culture period, the maximum average of 18750 CFU/ml water bacteria was observed in the 200 m cage station before the cage culture period and the minimum average of 3250  CFU/ml water bacteria was observed in the 200 m cage station at the end of the cage culture period. The presence of total coliform and fecal coliform in water samples was recorded as 18.75 and 2.08%, respectively, and fecal streptococcus water was not observed in any of the sampling stations and in this situation, fish cages culture did not cause contamination. Maximum and minimum water temperature, pH, turbidity, saturation percentage and biological oxygen demand are 26.50 and 7.00 °C, 8.71 and 8.29, 19.71 and 0.52 NTU, 87 and 160, respectively. Percentage of 1.32 and 8.39 mg/l were recorded. Based on the principal component analysis (PCA), the results showed that the variables of pH and water temperature had the highest variance and the total count along with water turbidity in the third component showed a significant positive correlation (p<0.05). As a result, the proper slope of the area, the proper flow of water around the small-scale cages has reduced the microbial contamination in the shade of the cage compared to the stations outside the cage.