The effect of salinity on survival and growth of the freshwater stenohaline fish spotted snakehead Channa punctata (Bloch, 1793)

摘要

Two independent experiments were performed to determine effects of salinity on survival and growth of adult Channa punctata.The purpose of the first one was to determine the median lethal salinity (MLS-5096h) and that of the second one was to assess survival and growth of the fish at different sub-lethal salinities under field conditions. 5,10,15,18 and 20gl~(-1) salinities were used initially to determine the range of salinity tolerance. After 100% mortality had been obtained at 20 gl~(-1)in the firstphase, a definitive salinity tolerance test was carried out in the next phase to find out the median lethal salinity by direct exposure of the test species to 10-18 gl~(-1) salinity for 96 h. The estimated MLS-50_(96h) for C. punctata (11.50 cm length; 12.05 g weight) was 13 gl~(-1) In the second experiment, survival and growth performances of the fish were recorded at two sublethal salinities viz., 5 and 10 g I-', along with those in fresh water as a control. Salinities up to and including 10 gl~(-1) did not affect growth performances significantly, the highest being recorded at 5 gl~(-1) salinity. Survival of the fish significantly depended on salinity, decreasing to 88.33% at exposure to 10 gl~(-1) salinity. Results of the present study indicate that C. punctata exhibits good tolerance to low salinities only (<10 gl~(-1)) demonstrating that it is a stenohaline freshwater fish. In conclusion, C. punctata can be considered as an ideal species to promote in view of current and future climate variablesas more and more coastal areas of India are going to be vulnerable to saline water inundation.