The combined effects of salinity and temperature on the egg hatching rate, incubation time, and survival until protozoal stages of Metapenaeus monoceros (Fabricius) (Decapoda: Penaeidae)

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The combined effects of 3 different temperatures (24, 28, and 32 °C) and salinity levels (35, 40, and 45 g L^{-1}) on the egg hatching rate, incubation time, larval activity, and survival rate until protozoal (PZ1) stage of Metapenaeus monoceros (Fabricius) were investigated under controlled laboratory conditions. The average fertilization rate was 97.25% following spawning. The eggs were stocked in 2-L glass larval culture flasks and received 1 of 9 salinity and temperature combinations in 3 replicates. The eggs hatched in all treatments. Temperature, salinity, and their interaction had significant influences on the hatching rate of the eggs (P < 0.05). The hatching rate decreased as salinity increased and was lowest in all temperature levels at a salinity of 45 g L^{-1}. With regard to the hatching rate, the best combinations were obtained at 35 g L^{-1} and 32 °C (91.67%) and at 35 g L^{-1} and 28 °C (89.17%). The incubation time was shorter at 32 °C (11.2 h) than at 28 °C (14 h) or 24 °C (17.2 h). The development rate from the naupliar stage to the protozoal stage was best at a salinity level of 35 g L^{-1} combined with temperatures of 28 °C and 32 °C. Larval activity was also found to be best at 28 °C and 32 °C at 35 g L^{-1} and 40 g L^{-1}, as compared to that at 24 °C in all salinity levels.