Effect of some minerals on shell hardening of mud crab, Scylla serrata (Forskal, 1775)

Abstract

Study on optimum requirements of some minerals in shell hardening of mud crab, Scylla serrata was carried out during the present study. Juveniles of live mud crabs in the size range of 73 – 94 mm carapace width and weight range of 110-160 g were stocked in HDPE circular tanks of 125 L capacity. The experiment was carried out in two phases according to the completely randomized design having three replicates for each treatment. At first phase, the pre-moult crabs were subjected to water of various composition and concentrations of minerals such as CaCO3 and KCl (each @ 500 to 800 mg L-1 at the interval of 100 mg L-1) and MgSO4 (1400 to 1700 mg L-1). At second phase, the experiment was conducted with increased concentrations of minerals such as CaCO3 and KCl (each @ 800 to 1100 mg L-1 at the interval of 100 mg L-1) and MgSO4 (1700 to 2000 mg L-1). The results revealed minimum shell hardening period of 9 ± 0 days and 9 ± 0.58 days in the first and second phase in the water having mineral contents of CaCO3 and KCl each at 800 mg L-1 and MgSO4 at 1700 mg L-1 respectively.