RESUMEN
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, Epinephelus summana, 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 E. summana 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.
RESUMEN
The aim of this study was to evaluate the use of dried marine seaweed, Gracilaria arcuata for the first time as dietary ingredient in partial substitution of fishmeal on the growth performance, feed utilization and body composition of African catfish, Clarias gariepinus. Four experimental diets were formulated: D1 as a control group; D2; D3 and D4 which included 10%, 20% and 30% G. arcuata meal respectively. One hundred and eighty African catfish weighing 9.62 ± 0.42 g, (mean ± SE) was divided into four groups corresponding to the different feeding regimes. The final body weight of the fishes showed significant differences (P < 0.05) between the control (D1); D2 and other treated groups D3 and D4, with weights of 66.98, 59.60, 47.34 and 30.73 g recorded for D1, D2, D3 and D4, respectively. Significant differences (P < 0.05) were also evident in weight gain, specific growth rate, and feed utilization between treatment and control groups. However, no significant differences (P > 0.05) were observed between the control group and fishes fed D2 for all previous parameters. Protein productive value, protein efficiency ratio, daily dry feed intake and total feed intake were also significantly lower in fish fed with a diet containing G. arcuata than in the control group and D2 which contains 10% of G. arcuata. Overall, the results of the experiment revealed that African catfish fed a diet with G. arcuata included in 20% and 30% levels showed poorer growth and feed utilization than the control group and D2. However, the study recommended that C. gariepinus can accept this ingredient up to 10% in their diets. More defined experiments therefore seem to be necessary in order to determine the maximum level of this marine seaweed in diets with amino acid supplementation for African catfish.