The reproductive biology of the mantis shrimp ErugosqviUa massavensis inhabiting the Mediterranean Sea at Port Said was studied and compared to previous studies. A single reproductive period was observed for females that lasted from February to August. This was followed by a well-defined resting phase from September to November, The ratio of males and females was nearly equivalent (0.95 female: 1 male). Females outnumbered males in all months except during the reproductive season. Gonad indices as well as the number of females with developed cement glands were relatively high during the spawning season. The body size at which 50% of females were sexually mature was much smaller than that reported in a previous study (22.6 mm CL and 25.7mm CL respectively). Females responded to extensive exploitation by reaching maturity at a smaller size and by increasing fecundity. The mantis shrimp population in Port Said appears so far seriously heavily exploited and needs urgent management regulations for the maintenance of that valuable fishery resource.