Assessment of gonadal development in large yellow croaker (Larimichthys crocea) cultured in saline-alkali water of Ningxia

The large yellow croaker (Larimichthys crocea) is an economically important marine fish in China. In order to explore the feasibility of inland saline-alkaline water aquaculture, this study systematically compared the effects on gonadal development of 14-month-old large yellow croaker, cultured in two different culture environments (offshore seawater in Ningde, and indoor saline-alkaline water in Ningxia). The evaluation was conducted on multiple parameters, including growth parameters, gonadosomatic index, sex ratio, gonadal histology, sex hormone levels (progesterone, estradiol, testosterone), and gonadal transcriptomes. The results showed no significant differences in growth and gonadal development between the two environments, with both ovaries at early developmental stages (phase I–III oocytes) and testes fully mature with abundant sperm. However, saline-alkaline water culture significantly reduced gonadal estradiol and testosterone levels in females, while increased progesterone levels in males. Transcriptomic analysis revealed a striking sex-specific response: females exhibited 8,744 differentially expressed genes (6,518 up-, 2,226 down-regulated), whereas males showed only two upregulated genes. GO and KEGG enrichment analyses of female differentially expressed genes indicated profound effects on energy metabolism, ovarian steroidogenesis, and cell cycle pathways. qRT-PCR validated the RNA-seq results. In conclusion, the saline-alkaline water environment in Ningxia does not impair gonadal development of large yellow croaker up to 14 months of age. Females undergo extensive transcriptomic reprogramming and hormonal changes, while males remain transcriptionally stable. These findings support the feasibility of the “marine fish inland farming” model, which alleviates pressure on coastal aquaculture, utilizes underappreciated saline-alkaline water resources, and promote coordinated regional development.