Background. Understanding of reproduction of the Egyptian sole, Solea aegyptiaca, has been considered a major step toward understanding its population dynamics, especially in the eastern Mediterranean Sea. In Egypt this species has highly commercial value and it has recently been successfully bred in aquaculture, but more data on the reproductive biology is still needed. So, the present work aimed to study the population structure and the reproductive dynamics of S. aegyptiaca over an annual reproductive cycle. Materials and Methods. A total of 594 specimens of S. aegyptiaca were obtained from October 2004 to September 2005 in a monthly basis from the commercial catch. Sex ratio, age, and length at first maturity, gonado- somatic index, maturity stage, oocyte diameter, and fecundity were analysed in order to increase our knowledge on the reproductive dynamics of S. aegyptiaca. Results. The overall ratio between males and females was 1.0 : 1.15 and showed no significant deviation from the expected 1 : 1 ratio, males are dominant among small size, while females are dominant among larger size. Females attained their maturity at the length of about 15.0 cm. The reproductive activity of S. aegyptiaca took place between January and June with a peak on January, when the majority of oocyte growth (> 400 μm in diameter) occurred. Hydrated oocytes reach 1000 μm immediately before spawning. Absolute fecundity ranged from 9898 to 38505 and can be expressed as a function of total length. Conclusion. S. aegyptiaca is a winter spawner, and the female attains its maturity at 15.0 cm of total length. So, fishing should be prohibited during the period from January to June to conserve the existing stock of the target species. Regulations should also be directed to reduce the fishing potential of 18.0 cm total length. It is important to give each fish the chance to reproduce at least once in its lifetime.
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