Production of neomale and neofemale large yellow croaker (Larimichthys crocea) and establishment of all-female populations

The large yellow croaker (Larimichthys crocea), with an XX/XY sex-determining system, is a key mariculture fish in China. The monosex culture of this species has economically advantageous due to distinct sexual growth dimorphism, requiring sex control technologies. This study aimed to produce neomale (XX♂) and neofemale (XY♀) fish by inducing sex-reversal in large yellow croaker and utilize neomales (XX♂) to create all-female populations. Letrozole (LTZ; 10 mg/kg) and 17β-estradiol (E2; 2 mg/kg) were orally administered to the fish (45 days post-hatching, dph) for 80 days to induce sex-reversal. LTZ treatment resulted in 91.1% masculinization and E2 treatment resulted in 93.5% feminization. E2 treatment significantly inhibited the growth while no significant difference was observed in the the LTZ group and the control. Furthermore, Sex-reversal in large yellow croaker was confirmed by distinct expression patterns of two sex-related genes, dmrt1 and cyp19a1a. Subsequently, neomales were crossed with control females upon reaching sexual maturity, facilitating the large-scale production of all-female populations. These results underscore the viability of sex-reversal methods in large yellow croaker and the potential for mass-production of all-female populations, thereby establishing a groundwork for monosex culture in this species.