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Response of macrobrachium rosenbergii (de Man) to calcium and magnesium concentrations in freshwater
(Department of Aquaculture, College of Fisheries,Panangad, 2000) Sivakumar, T V; KAU; Mohankumaran Nair, C
The effect of various concentrations of calcium in freshwater on growth, survival, food intake and food conversion ratio of M. rosenbergii post larvae were investigated in order to arrive at the optimum range of calcium required in freshwater for successful culture. In two stage-designed experiment, the first experiment was bioassay for three days, in order to understand maximum and minimum tolerance level of calcium and magnesium. The Le-50 of calcium and magnesium in freshwater was found to be 1562.85 and 7823.48 mg/l, respectively. Based on the results of bioassay, the rearing experiment was carried out in circular fiberglass tanks for calcium alone. The levels used were 5, 10,20,50, 100,200,300, 400, 500, 600, 700 and 800 mg/l, i.e. 12 treatments and for each treatment two replication were used. Growth was maximum at 400 mg/l of calcium in freshwater. Better food conversion ratio and survival were also obtained at this level. The growth declined in lower and higher concentrations of calcium, but the survival remained above 80% up to 400 mg/l and later on it got reduced as the concentration of calcium increased. The food conversion ratio increased at lower and higher levels of calcium.