Effect of Mineral Supplement (Ca, Mg and K) in Water on Developmental Stages and Survival Rate of Mud Crab (Scylla paramamosain Estampador, 1949) Larvae

Abstract

To improve larviculture of mud crab (Scylla paramamosain), we determined the impacts of calcium (Ca), magnesium (Mg) and potassium (K) supplementation in water on the development and survival rates of crab larvae in the zoea (Z1-Z5), megalopa (M) and first crab (C1) stages. Four water treatments (each with 3 replications) were used in experiments: 1) without any addition (control); 2) with 400 mg·L^-1 Ca supplement (T1); 3) with 1,350 mg·L^-1 Mg supplement (T2); and 4) with 380 mg·L^-1 K supplement (T3). Minerals were added to the experimental tanks every three days. The results showed that the developmental stages of crab larvae from Z1-Z2, Z2-Z3, Z3-Z4, Z4-Z5, Z5-M and M-C1 were not significantly different in any of the treatments or the control, and the range in larval development from the Z1-C1 stages in all treatments was 24.8±0.3-25.8±0.3 days. No significant differences were observed for the survival rates of the Z1 to Z5 stages in each treatment. However, supplementation with Ca (T1) and Mg (T2) resulted in significantly higher survival rates of the M (19.8±2.8 and 16.5±2.6 %, respectively) and C1 (4.7±2.7 and 4.8±1.1 %, respectively) stages than that of the respective control (7.6±3.2 % for M stage and 1.5±0.8 % for C1 stage). On the other hand, the survival rate of the M and C1 stages in T3 (K supplement) (10.8±6.2 and 2.1±0.3 %, respectively) were not significantly different from the control. The conclusion was drawn that supplementing either Ca or Mg in rearing water increased survival rates of S. paramamosain larvae in the M to C1 stages.