The population of the portunid crab Charybdis natator in the Gulf of Suez,Red Sea was studied by monthly sampling from September 2007 to May 2008. Crabs were sexed, measured and berried females recorded. A total of 498
individuals were obtained, of which 232 (46.6%) were males, 212 non-ovigerous females (42.5%), and 54 (10.9%) ovigerous females. The overall sex ratio (M:F) was (1:1.1) and females outnumbered females during September-November. The population showed sex differences in the size frequency distributions, with males reaching larger size than females (70-148.4mm and 47.5-130.5mm CW, respectively). Ovigerous females existed all year round and ranged in size between 83-118.4mm CW. Fecundity ranged from 45230 to 335529 eggs per female and was positively correlated with body size. The effectiveness of the closed season that runs in the Gulf of Suez on the population of C. natator was
discussed.