Effect of different salinity levels on egg hatching and survival rate of different metamorphosis larval stages of Kuruma shrimp, Penaeus japonicus (Bate, 1888)

The effect of six different salinity levels was studied on egg hatching percentage and survival rate of different larval stages of the Kuruma shrimp, Penaeus japonica. Eggs of the Kuruma shrimp and different larval stages included nauplius, zoea, mysis, and postlarvae were stocked at experimental glass vessels (2 L) in replicates for each treatment at a density of 50 per replicate. The different stages were evaluated under different water salinity levels included 20, 25, 28, 30, 35 and 38 ppt. All vessels were supplied with continuous aeration. Kuruma shrimp stages were fed during the experimental period with micro-algae, rotifers, and Artemia on a live food program. Some physico-chemical parameters included temperature, salinity, pH, Turbidity, TAN, NH₃, and DO were determined during the experimental period (23 days). The data of the eggs hatching percentage and survival rate of the different larval stages of Kuruma shrimp reared in different tested salinity levels showed that all stages reared in 20 ‰ salinity level gave the lowest survival rate in compared to those reared in 38 ‰ and the other tested salinity levels without significant differences (P < 0.05). Increasing the water salinity levels in the culture water over 20 ‰ resulted in an improvement in survival rate in all tested larval stages especially on 38 ‰, it was the best survival rate between all tested salinity levels in the Nauplius stages (N₁- N₆), Zoea stages (Z₁- Z₃) with significantly differences (P < 0.05). Also, the best survival rate was in 38‰ with significant differences (P < 0.05) for Mysis stages (M₁- M₃), Data showed that the highest tested salinity level (38 ‰) gave the higher survival rate to post larvae of the kuruma shrimp included 94%, 85%, and 80%, for PL₁, PL₆, and PL₁₂, respectively. The results showed that the survival rate for all larval stages was obtained in 38 ‰ salinity levels. Therefore, it could be recommended for applying and extending out these results under Egyptian conditions.