Masculinization of Northern Pike Fry Using the Steroid 11 β-Hydroxyandrostenedione

Abstract

Morphological and histological studies of gonads demonstrated that 11 β-hydroxyandrostenedione (11 β-HA) can be used to control the phenotypic sex in northern pike Esox lucius. Oral administration of 11 β-HA (30 mg/kg pelleted food) to northern pike juveniles (average total length ± SD = 2.80 ± 0.18 cm) for 2 weeks resulted in sex reversal of most of the females and produced a stock that consisted of 87% males and 13% bisexual animals. Testes of hormone-treated fish possessed seminal ducts and were characterized by a regular morphology, but histological observations showed that germ cells differentiated earlier in ontogeny than we observed in the gonads of untreated fish. Gonads of bisexual fish were morphologically ovaries or testes but in either case contained both female and male germ cells, although in some individuals atrophy of individual oocytes was observed. We obtained practical information on effectiveness of the androgen application (timing, duration, and dose) to northern pike juveniles.