International Journal of Fisheries and Aquatic Research

Authors
Azhar Ali, MS Khatun, S Bikash Saha, MNS Mamun Siddiky, D Kumer Mondal, S Lutfor Rahman

Abstract
An experiment was conducted to standardize dose of chlorine for improving sanitation of shrimp (Penaeus monodon) culture in brackishwater ponds in modified extensive system over a period of 120 days from 27 March 2013 to 25 July 2013. The experiment designed with four treatments whereas one treatment is a control of without any chlorine dose and other three treatments designed with three chlorine doses such as T1 (No chlorination), T2 (3 ppm), T3 (6 ppm) and T4 (9 ppm) each with three replicates. Total bacterial load reduced after application of chlorine. After chlorination at 3-9 ppm, about 82-85% total bacterial load was reduced. Increase in concentration of chlorine concentration showed no significant reduction of bacterial load. But after two days, bacterial load again started to increase. Load of total coliform also reduced drastically after application of chlorine at the same rate. The mean final weight of shrimp was 18.89±1.20, 17.90±0.50, 19.25±0.53 and 19.00±0.66 g in T1, T2, T3 and T4, respectively. The highest mean survival was recorded in T1 (77.16±4.41%) followed by T2 (77.09±4.26%), T3 (63.61±3.35%) and T4 (64.24±3.25%). The highest production was recorded in T1 (730.73±87.55 kgha^-1) which was significantly differed from (p < 0.05) T2, T3 and T4. Higher concentration of chlorine also showed no negative impact on the growth of shrimp but mortality of some moulted shrimp was observed. The present study, it was revealed that increasing the chlorine doses, decreasing the production and without chlorination highest production was recorded.