Evaluating the reproductive performance of Summan grouper, Epinephelus summana (Forsskal, 1775), in the Red Sea

Grouper fish are among the most important components of the fisheries of many countries because they are found in warm water throughout the world. There are 15 genera and 159 species known worldwide; 8 genera and 66 species are exclusively found in the western Indian Ocean, Red Sea, and Arabian Gulf. The Summan grouper, <i>Epinephelus summana</i>, constitutes a considerable portion of these fisheries; therefore, this study aimed to evaluate the reproductive strategy of this important fish species. The fish samples were collected monthly for one year (from November 2020 to October 2021), and 217 fish were collected from the Red Sea of Jeddah, Saudi Arabia. The sex ratio, sexual maturation process, and spawning season were analyzed. Across all samples, landing consisted of 36.2 ± 4.7 % males, 64.0 ± 5.0 % females, and 3.4 ± 1.8 % transitional-stage fish, with an overall significantly different male-to-female sex ratio of 1:3.3. Furthermore, males were larger than females. The maturation index (MI), gonadosomatic index (GSI), and ovarian maturation rate (OMR) values fluctuated throughout the year, indicating that <i>E. summana</i> has extended spawning and spawns in batches during different months of the year. However, April to May is the main spawning season, with the highest female GSI recorded. Based on the microscopic histological examination of gonads, the maturation process can be classified into five stages in both males and females. In conclusion, this fish species has a complex reproductive biology. It undergoes sexual transformation and protogynous hermaphroditism, during which individuals mature first as female and then change sex to male. The obtained data is essential for successful fishery stock conservation, management, and aquaculture development.