Objective This study aims to explore the histological characteristics of early gonadal differentiation and development of Siniperca scherzeri, enrich the reproductive biology data of this species, and provide a theoretical basis for mono-sex breeding.

Method Artificially bred S. scherzeri aged 2 to 62 days post-hatching (dph) were taken as the research objects, and 15 individuals were sampled every 5 days. Gonadal tissue sections were prepared by paraffin embedding sectioning and hematoxylin and eosin (HE) staining techniques. These sections were observed, photographed and measured using an Olympus FX380 microscope and CaseViewer 2.4 software.

Results The primitive gonads of S. scherzeri had already formed at 7 dph, distributed in pairs on the coelomic membrane between the mesonephric ducts and the intestines. For male S. scherzeri, the spermaduct anlage and primary spermatocytes were observed at 17 dph and 27 dph, respectively, marking the beginning of anatomical and cytological differentiation of the testis. The testis of S. scherzeri belonged to lobular structure, and its development process was relatively rapid: it was at stage Ⅰ from 17 to 27 dph, entered stage Ⅱ at 32 dph, reached stage Ⅲ at 37 dph, and developed to stage Ⅳ at 62 dph. For female S. scherzeri, the ovarian cavity and primary oocytes were observed at 22 dph and 32 dph, respectively, marking the beginning of anatomical and cytological differentiation of the ovary. Ovarian development was comparatively slower: remaining at stage Ⅰ from 22 to 42 dph, and progressing to stage Ⅱ from 47 to 62 dph.

Conclusion Under natural water temperature conditions, primitive gonads of S. scherzeri had formed within one week after hatching, and the developmental process of testis was significantly faster than that of ovary. At 62 dph, the testis had developed to stage Ⅳ, while the ovary had only reached stage Ⅱ. This study on the early gonadal differentiation and histological development characteristics of S. scherzeri could provide a theoretical foundation for the development of mono-sex breeding techniques for this species.