Effect of salinity on survival and growth of giant freshwater prawn Macrobrachium rosenbergii (de Man)

Abstract

Two independent experiments were performed to determine the effects of salinity on survival and growth of juvenile Macrobrachium rosenbergii, first one was to determine the median lethal salinity (MLS-5096h) and second one was to assess the survival and growth at different sub-lethal salinities under field condition. In MLS-5096h study 0, 5, 10, 15, 20, 25 and 30ppt salinities were used to initially find out the salinity tolerance range. Accordingly, a definitive salinity tolerance test was done in next phase to find out exact median lethal salinity by directly transferring the test species to 21, 22, 23, 24, 25, 26 and 27ppt salinity for 96h. The median lethal salinity of M. rosenbergii was estimated at 24.6ppt. In the second experiment, survival and growth performances of the prawn were recorded at different sub-lethal salinities viz., 5, 10, 15 and 20ppt along with 0ppt as control during 60 days culture period. The prawn exhibited lowest final average weight at 20ppt salinity and significantly highest at 10ppt salinity. Highest SGR and weight gain were obtained at 10 ppt followed by 5ppt, 15ppt and 0ppt salinity but differences among treatment were not significant (P>0.05). Survival rate of prawn varied between 91% (at 0ppt) and 78% (at 20ppt). The prawn grew and survived satisfactorily at 0–15ppt salinities, implying that the species can be cultured commercially at wide salinity range. M. rosenbergii can be considered as an ideal species to promote, in view of current and future climate variables as more and more coastal areas of India are going to be vulnerable to saline water inundation.