| The tomato hind, Cephalopholis sonnerati, a high-value marine species endemic to the South China Sea, is renowned for its economic significance and market potential. Despite its importance, researches on this species have primarily focused on spawning behavior, reproductive patterns, and genome assembly. This study systematically investigated gonadal development and the muscle nutritional composition of C. sonnerati across its gonadal development stages, aiming to elucidate its biological characteristics and nutritional value, thereby supporting its aquaculture development. The histological observations of C. sonnerati gonads revealed distinct patterns of gonadal development. During the first three months, gonadal development progresses slowly. From four months onward, the development rate increased significantly from 4 to 13 months of age. The gonadal somatic index (GSI) remained stable during this process but showed a significant increase in broodstock at the mature gonadal stage (stage V). Mature gonads exhibited high degrees of development, supporting robust reproductive capability. These findings established a clear timeline for the reproductive maturation of C. sonnerati and underscored the importance of tailored aquaculture practices during these critical stages. To further understand the implications of gonadal development on nutritional status, this study analyzed muscle composition across five gonadal development stages (I–V). Key parameters such as water, protein, and lipid content were evaluated. The results revealed that water and protein content showed a continuous increase from stage I to stage V. Lipid content peaked during stage IV but declined significantly at stage V. This pattern indicates heightened metabolic activity during the reproductive phase, where lipids are mobilized to support gonadal development. Lipids and proteins, as primary energy sources, play crucial roles in sustaining growth and reproductive maturation. At stage V, C. sonnerati achieved its maximum crude protein content (21.27 ± 0.21) g, a value notably higher than that of most other marine fish species (commonly 13.90–21.03 g) and reported groupers. This finding highlighted C. sonnerati as a premium high-protein marine fish, with significant implications for its commercial value. A total amino acid content in C. sonnerati muscle ranged from (18.20 ± 0.26) % to (19.63 ± 0.06) %, encompassing all seven essential amino acids (EAAs) required for human health. The essential amino acid index (EAAI) of C. sonnerati exceeded that of most other economically significant fish species. The ratio of EAAs to total amino acids (EAA/TAA) ranged from (39.34 ± 0.34) % to (40.49 ± 0.24) %, closely aligning with the FAO/WHO ideal value of 40%. Similarly, the ratio of EAAs to non-essential amino acids (EAA/NEAA) was (75.98 ± 0.74) % ~ (80.33 ± 0.85) %, significantly higher than the FAO/WHO recommended standard of 60%. Compared with stage I to IV, nutritional quality peaked in muscle of stage V broodstock. Furthermore, C. sonnerati was found to contain six flavor-related amino acids, with their total content ranging from (8.76 ± 0.10) % to (9.24 ± 0.08) %, surpassing levels found in other grouper species. This indicated that C. sonnerati not only possessed high nutritional value but also offered superior taste quality. Using amino acid scores (AAS) and chemical scores (CS), methionine (Met) and cysteine (Cys) were identified as the first limiting amino acids in C. sonnerati, while valine (Val) was identified as the second limiting amino acid. These findings suggested that supplementing these amino acids in aquaculture feed formulations could significantly enhance growth and reproductive performance in C. sonnerati. In addition to amino acids, 25 fatty acids were identified in the muscle tissue of C. sonnerati. Palmitic acid (C16:0) and oleic acid (C18:1) were the most abundant but showed a declining trend during gonadal development, indicating their mobilization and transfer to support oocyte maturation and reproductive energy metabolism. In contrast, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) levels reached their peak during stage V, with levels exceeding those reported in most marine fish species. This highlighted their pivotal role in energy supply during reproduction and their potential health benefits for human consumption.Mineral composition analysis revealed that C. sonnerati muscle contained five major macroelements: phosphorus, magnesium, potassium, sodium, and calcium. Among trace elements, zinc and selenium were found in significant quantities across all developmental stages. Selenium content, particularly high in stage V broodstock, was superior to that of other groupers. Selenium is known for its vital roles in enhancing immune function, preventing cardiovascular diseases, and improving antioxidant activity. The combination of high selenium levels and abundant other minerals such as phosphorus and magnesium positioned C. sonnerati as an excellent dietary source of essential nutrients. The comprehensive nutritional evaluation of C. sonnerati underscored its value as a high-quality marine fish species. Rich in essential amino acids, fatty acids, and minerals, C. sonnerati demonstrated exceptional nutritional and health-promoting properties. Its superior protein content, coupled with its abundance of DHA, EPA, and selenium, make it particularly suitable for human consumption and a promising candidate for aquaculture promotion. The findings of this study not only emphasized the dietary and economic potential of C. sonnerati but also provided critical insights for optimizing its aquaculture practices. By understanding the nutrient mobilization patterns during gonadal development, aquaculture practitioners can develop stage-specific feeding strategies to enhance growth, reproductive performance, and overall fish quality. Furthermore, the identification of limiting amino acids suggests opportunities for improving feed formulations to support optimal development. In conclusion, C. sonnerati represented a highly nutritious and economically valuable species with immense potential for sustainable aquaculture development. Its rich nutritional profile, superior muscle quality, and high protein content position it as a premium product in the seafood market. The results of this study served as a valuable reference for the formulation of efficient aquaculture feeds tailored to different developmental stages of C. sonnerati, contributing to the broader goal of advancing sustainable marine aquaculture. |
