Abstract:In this study, oocyte characteristics were observed during ovarian development of the spotted steed ( sampled from 2015 to 2017, under light and scanning electron microscopy. A total of 190 fish were sampled, with body length between 7.12 cm and 32.21 cm and body weight between 10.55 g and 330.22 g. Our results showed that oocyte development can be divided into five distinct stages. Oocytes in phase I are considered to be in an oogonial proliferation stage. The second phase of oocyte development for the spotted steed is equivalent to the primary growth stage, and this oocyte development stage is characterized by the presence of a follicular layer. Stage III is marked by the appearance of cortical vacuoles, and the zona radiata (ZR) can be differentiated from the follicular layer. Stage IV oocytes enter the late growth stage, and the yolk granules increase. In electron micrographs, the pore-like structures of the ZR were clearly observed, which are believed to be related to nutrient accumulation. Stage V oocytes are characterized by mature oocytes and a completely degenerated nuclear membrane. Following ovulation, the space between the oocyte and ovary membrane is evident. During the reproductive season, the gonadosomatic index (GSI) ranged from 13.78% to 17.04%. The obtained data will consequently facilitate the artificial propagation and breeding of this commercially important species.