Induced sex reversal using an aromatase inhibitor, Fadrozole, in Atlantic halibut (Hippoglossus hippoglossus L.)

Production of all-female Atlantic halibut (Hippoglossus hippoglossus L.) is desirable for the industry because of sexual growth dimorphism existing in this species. The first step towards establishing monosex all-female cohorts is to produce sex-reversed females (neo-males). The objective of this study was to test the efficiency of an aromatase inhibitor, Fadrozole, to induce masculinisation in Atlantic halibut. Three doses of Fadrozole were tested: 100, 500 and 700 mg/kg of feed, applied for 42–60 days to weaned halibut fry of 26–30 mm TL. All tested doses proved to be efficient, resulting in the development of testes in up to 97% of examined individuals. Seventeen-α-methyltestosterone (MT) was used as a positive control. MT-treated fish were all males. No abnormalities in the development of gonads were observed in any of the groups. Analysis of 11-ketotestosterone (11KT) blood plasma levels showed that most of individuals in the experimental groups had 11KT levels typical for males while controls had 11KT levels typical for males or females.