Knowledge of the inherent reproductive patterns of wild prawn populations is essential in predicating the expected
performance of hatchery broodstock. During the four year study 1995-1998, assessment was made for broodstock of P. japonicus collected from the wild (AbuKir bay, Alexandria) over all spawning season (May-December). The reproductive performance of the broodstock was assessed on the bases of spawning process, egg production, nauphii production and hatchability rate in relation to size and weight of spawners. The results of spawning performance and larval
survival showed that among 179 specimens ranging in size from 13.0 to 23.0 cm in total length utilized for spawning, 134 specimens were succeeded for spawning (75 %). Higher percentages of full spawning (41%) and partially spawning (11.9 %) groups were observed in prawns belonging to the size group 15.0 ~17.0 cm in total length. The maximum
number of eggs produced per female was 545,000 by full spawner of P. japonicus at 16.6 cm total length during the period May, July 1998. Higher hatchability rate (81%) from eggs to nauplius stages was recorded with spawners of the size group from 17.0~19.0 cm total length in average during the four years of study. The survival rate from nauplius to
first post larvae (PL1) for full and partially spawned females were recorded for the same size group 17.0 ~I 9.0 cm and this size is expected for prawns of an age about 12 months old. May, June and July are considered the most active period for an effective spawning of P. japonicus in Egyptian Mediterranean water followed by another active spawning period in October-December. Water temperature was found to be the most effective environmental parameter for the active spawning performance of the investigated species.