Seasonal Variation of Bacterial Flora in Ponds in Saudi Arabia Usedfor Tilapia Aquaculture

摘要

The seasonal bacterial flora of fish ponds were quantitatively and qualitatively examined at quarterly intervals for one year from April 2001 to March 2002 for the first time in Saudi Arabia and the isolates were identified to the species level. Total viable count of bacteria in pond water ranged from 7.8 plus or minus 0.9 X 10 super(3) to 1.3 plus or minus 1.1 X 10 super(4) cfu/mL in Summer (33.0 plus or minus 2.3 degree C); 5.1 plus or minus 1.7 X 10 super(3) to 2.2 plus or minus 1.0 X 10 super(4) cfu/mL in Fall (24.1 plus or minus 1.9 degree C); and 6.7 plus or minus 2.1 X 10 super(2) to 2.5 plus or minus 0.6 X 10 super(3) cfu/mL in Winter (14.5 plus or minus 1.5 degree C). In total, 21 different species of bacteria from 19 different genera were isolated. The predominant microflora consisted of gramnegative rods. In all seasons, Aeromonas hydrophila, Shewanella putrefaciens, Corynebacterium urealyticum, and Escherichia coli were the most prevalent bacteria. Flavobacterium sp. and Pseudomonas spp. were dominant only in the winter. Pasteurella spp. were also consistently isolated throughout the sampling period. Bacteria present seasonally were Pseudomonas spp., Flavobacterium sp., Cellulomonus sp., and Micrococcus sp. Ambient seasonal temperature variation could account for some of the bacterial population variation. Presence of fecal coliform bacteria in the fish-culture waters suggests that care should be practiced during processing the fish caught from these waters to prevent contamination of edible meat.