Novel Method for Preparing Pseudo-Male Common Carp by Inducing Secondary Female-to-Male Sex Reversal Under High Temperature Conditions

For economically viable fish species that exhibit sexual dimorphism in growth performance, such as common carp, cultivating monosex populations is an effective approach to enhance aquaculture yields. This method for producing an all-female carp population involves inducing pseudo-male carp through exogenous androgen/estrogen inhibitor administration, followed by crossing these pseudo-males with wild-type female carp to generate all-female offspring. However, the sex reversal effect induced by exogenous androgen/estrogen inhibitors is unstable, making the maintenance of these pseudo-male broodstocks a time-consuming and labor-intensive process, and posing a risk of aquatic environmental contamination. High temperatures can efficiently induce pseudo-males in Indian carp (Cyprinus carpio L). However, we achieved little success when applying the same method to Yellow River carp. In this study, we systematically tested the effects of different high-temperature treatment periods on sex reversal in Yellow River carp, a geographically distinct strain of common carp (Cyprinus carpio) endemic to the Yellow River basin in China. High-temperature treatment, before and after sexual differentiation, genetically female carp were induced to develop into phenotypically male with functional testes. Furthermore, sex-differentiated female Yellow River carp are more sensitive to high temperatures, making them more prone to reversal. Therefore, a novel method for the production of pseudo-male Yellow River carp was established by inducing secondary sex reversal through high-temperature exposure. Pseudo-male carp prepared using this method possessed a stable sperm-production capacity. Our study provides a novel strategy for cultivating all-female carp populations.