Sexing of farmed immature beluga (Huso huso) using steroid hormone levels as indicators

Abstract In order to avoid the invasiveness of sexing associated with biopsy in beluga (Huso huso), we explored the possibilities of using sex steroid levels to determine the sex of farmed immature fish. Belugas were selected randomly from 2-, 4- and 5-year-old stocks, cultured under the same enviro...
Ausführliche Beschreibung

Abstract In order to avoid the invasiveness of sexing associated with biopsy in beluga (Huso huso), we explored the possibilities of using sex steroid levels to determine the sex of farmed immature fish. Belugas were selected randomly from 2-, 4- and 5-year-old stocks, cultured under the same environmental and feeding regimes. Conventional methods of sexing by biopsy and histological observation were used to determine the sex and gonadal stage, while enzyme-linked immunosorbent assay was employed to measure the levels of testosterone (T) and 17β-estradiol ($ E_{2} $) in serum. All fish had differentiated gonads, and males and females could be distinguished microscopically in all age groups. T levels differed significantly between males and females but made for poor predictors of sex due to the substantial overlap in ranges of T levels in both sexes. There was no significant difference in $ E_{2} $ levels between males and females. When calculating the T/$ E_{2} $ ratios (TER), a clear separation was obtained for 5-year-old fish, ratios over 40 predicting male and those below 40 predicting female phenotypes. The study demonstrated that the TER can be used as an effective indicator to separate males and females in cultured immature 5-year-old beluga. Ausführliche Beschreibung