Cultivation of all-male large yellow croaker (Larimichthys crocea) and evaluation of its temperature tolerance and hypoxia tolerance.

Mono-sex cultures of all-male large yellow croaker (Larimichthys crocea) offers clear advantages for boosting economic returns in aquaculture. The purpose of this study was to breed all-male large yellow croaker. To achieve this goal, we first successfully induced sex reversal of YY supermale fish to produce YY pseudo-female through adding 17β-estradiol (E2, 120 mg/kg). These YY pseudo-female were then crossed with YY supermale fish to establish a pure-bred YY supermale fish population. Subsequently, the YY supermale fish were hybridized with female fish to produce all-male fish. During the breeding process, YY pseudo-female, YY supermale and XY all-male fish were identified by sex-specific molecular markers and gonad histological observation. The results showed that in the experiment of inducing sex reversal of YY supermale fish. The survival rate of YY pseudo-female fish was 63.4 %, and the hatching rate of its offspring pure-bred YY supermale fish was 68.06 %. There was no significant difference in growth, testes development stage, sex steroid hormone levels and the expression of testis development-related genes levels between pure-bred YY supermale and normal male fish. In the temperature tolerance assay, the all-male group exhibited significantly higher survival rates than the control under both high- and low-temperature stress. In the hypoxia tolerance experiment, the respiratory oxygen consumption rate of all-male fish decreased more with the decrease of dissolved oxygen in water, and the asphyxiation point was lower. It shows that the all-male fish is more adaptable to the adverse environment. In summary, it is feasible to obtain a pure-bred YY supermale fish population by inducing YY supermale fish sex reversal. On this basis, the all-male fish population can be produced, and the stress resistance advantages of all-male fish have considerable application potential for the aquaculture of large yellow croakers.