Comparative study on bacterial flora of the intestine in Persian sturgeon (Acipenser persicus) fingerlings reared in fiberglass tanks and earthen ponds

   Stability of bacterial flora in fish intestine is very important, because the intestine is an important organ for outbreak of microbial infections and other fish diseases especially when the fish have not been vaccinated. The aim of this study was to determine the bacterial flora of intestine in sturgeon juvenile in earthen ponds. The results can be applied to prevent the diseases occurrence and health management. In this study, 90 individuals of Persian sturgeon  ranged 3-5g in weight collected randomly by trawling in 3 earthen ponds as well as 15 individuals  ranged 10-20g in weight by small net in 3 fiberglass tanks. After recording morphometric characteristics, the intestine fish and rearing water were cultured on TSA medium. Gram staining and complementary tests were conducted. In order to identify the bacterial species, various biochemical experiments and diagnostic kits of API 20E (special for gram - negative bacteria) were employed. According to morphometric measurements, in earthen ponds the mean weight and length of juveniles were 5.59 ± 3.18 and 11.4 ± 2.9, respectively. The results showed that in these ponds the mean facultative aerobic and anaerobic bacterial counts in the juvenile intestine were 5.59 ± 0.92 (log CFU.g-1) compared to 6.67 ± 0.34 (log CFU.ml-1) in rearing water. Furthermore, the following bacteria were found in the intestine of Persian sturgeon: Aeromonas sp., A. sobria, A. hydrophyla, Entrobacteriaceae and Corynebacterium, while the bacteria recovered from the rearing water were Aeromonas sp. and A. sobria. According to   morphometric measurements, in the fiberglass tanks, the mean weight and length of juveniles were 12.13 ± 2.51 (g) and 15.11 ± 1.13 (cm), respectively. The results showed that in these tanks, the mean facultative aerobic and anaerobic bacterial counts in the fish intestine were  4.77 ± 0.04 (Log CFU.g-1) compared to 4.81 ± 1 (Log CFU/ml) in rearing water. Furthermore, the following bacteria were identified in the intestine of Persian sturgeon: Aeromonas sp., Micrococcus, Staphylococcus. The bacteria in the rearing water were A. sobria, Acinetobacter, Moraxella, Micrococcus and Staphylococcus.