The influence of salinity and management practices on the production ofPenaeus monodon and changes in the counts of total heterotrophs (THCs), presumptive vibrios (PVCs) and luminous vibrios (LBCs) in nine modified extensive brackishwater ponds was investigated for one crop period, ranging from 102 to 132 days. The THCs ranging from 104 to 106/ml pond water and 105 to 107/g pond sediment and PVCs from 102-105/ml pond water and 103-106/g pond sediment were recorded. The LBCs were detected only in high saline ponds in the range of 102-104/ml pond water and 103-105/g pond sediment. The results of the bacterial counts of low (4-9 ppt), medium (9-15 ppt) and high (15-26 ppt) saline shrimp ponds indicated that the THCs, PVCs and LBCs of water samples are influenced by salinity and their counts increased with increase in salinity. Although the production/ha among the ponds did not vary much (P>0.05), the farmers were to extend the culture period by about 12-18 days in low saline and 20-30 days in medium saline ponds compared to high saline ponds to attain a harvest size of 29-30 g. The results clearly indicated the positive effect of optimum salinity on the growth and the overall health status of shrimp, despite the higher counts of heterotrophs, vibrios and luminous vibrios in pond water and pond sediment.
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