Effects of salinity on growth and energy budget of juvenile Penaeus monodon

A growth trial was conducted at 28.8 ± 1.8 °C to investigate the effect of salinity on survival rates, specific growth rates (SGR), food conversion efficiencies (FCE) and energy parameters of Penaeus monodon. Juveniles of P. monodon with average weight 1.20 ± 0.05 g were cultured at salinities of 5, 10, 15, 20, 25, 30 and 35 psu. Results showed that survival rates of P. monodon were not significantly affected by salinity in the range 10–35 psu. However, the lowest and significantly different (p < 0.05) survival rate was observed at 5 psu. The highest SGR (3.24 ± 0.25%/d) and FCE (54.90 ± 2.97) were observed at 25 psu. Salinity had a strong influence on various energy parameters, namely energy deposited for growth (G), energy lost for respiration (R), energy lost in feces (F), energy lost in excretion (U) and energy lost in exuviae (E), but had little influence on feeding rate (FR). It indicated that growth rate differences under different salinities were not resulted from differences of FR, but mainly resulted from differences of assimilation efficiency and energy channeled into respiration. The highest net growth efficiency was attained at 25 psu, and a salinity range outside 20–35 psu increased the energy channeled to respiration, excretion and exuviae, which led to significant reduction in growth and feed conversion efficiency. Therefore, the optimum salinity for the culture of P. monodon appeared to be ~ 25 psu, where the average energy budget was: 1OOC (100% energy consumed in food) = 14.51(± 1.05)G + 66.68(± 1.56)R + 14.54(± 0.72)F + 3.33(± 0.24)U + 0.93(± 0.07)E.