Bacterial population in intensive tilapia (Oreochromis niloticus) culture pond sediment in Hai Duong province, Vietnam

Three intensive tilapia ponds were studied to determine the bacterial population during the culture period in Hai Duong province, Vietnam. Bacteria were identified to genus or species level. Total bacteria count in sediment ranged from 6.49 × 105 to 1.29 × 106 cfu g-1. In total, 11 bacterial genera and 13 species were identified from pond sediments, in which both gram-negative and gram-positive rod-shaped bacteria dominated the population accounting for 52 and 48%, respectively. Both beneficial and harmful bacteria were found in sediments, in which the harmful bacterial species dominated (62.5%) and appeared more at the beginning of culture. The harmful bacteria were Pseudomonas fluorescens, Pseudomonas sp., Vibrio pectenicida, Enterococcus, sp.HD31, Enterococcus sp.HD1, Vibrio damsella, Aeromonas sp.HD5, Vibrio sp. HD7, Vibrio sp.HD331, Aeromonas sp.HD361, Enterococcus sp.HD371, Vibrio sp.V31, Aeromonas hydrophyla and Pseudomonas putida. In contrast, beneficial bacteria accounted for 20.8% only of total isolates. The beneficial bacteria were Carnobacterium inhibens, Lactobacillus plantarum, Bacillus cereus, Lactobacillus delbrueckii and Bacillus pumilus; they appeared more in the later stage of culture period.   Key words: Bacteria, Oreochromis niloticus, intensive culture pond, sediment, beneficial bacteria, harmful bacteria.