Out-of-season artificial reproduction techniques of cultured female tongue sole (Cynoglossus semilaevis): Broodstock management, administration methods of hormone therapy and artificial fertilization

Abstract

The present study aimed at the development of an effective and efficient artificial reproduction technique for cultured female tongue sole (Cynoglossus semilaevis) in out-of-season. After about four-month enriching cultivation of broodstocks, a series of experiments were conducted to develop a protocol for the hormonal induction of ovulation and artificial fertilization. The results showed that single injection of combination of luteinizing hormone releasing hormone analogue (LHRH-A3), human chorionic gonadotropin (HCG) and domperidone (DOM) is effective to induce ovulation at different final maturation stages (i.e., stage IV and V). The optimal single injection dosages of combined hormones were (0.15 μg LHRH-A3 + 4 IU HCG + 2 mg DOM) / kg BW and (0.05 μg LHRH-A3 + 2 IU HCG + 1 mg DOM) / kg BW for females at stage IV and V respectively. At the optimized dose of hormones, the fertilization and hatching rates were 44.6% and 80.4%, 30.4% and 63.4% for stage IV and V respectively. The lapsed time to ovulation was very predictable and ranged from 35.5 to 39.5 h post injection. Ovulated eggs in ovarian cavity should be stripped within 15 min in order to obtain the highest fertilization and hatching rates, otherwise the values decreased significantly thereafter. These researches are expected to provide improved implementation of artificial reproduction techniques for the production of fertilized eggs in the commercial aquaculture of tongue sole.