Determination of sex and maturity in Acipenser stellatus by using ultrasonography

Abstract

Knowledge of both sex and maturity stage without killing fish is important from many aspects. The establishment of accurate sex and maturity determination without external sexual dimorphism or when external characters are not developed has usually involved the use of either hormone radioimmunoassay or biopsy techniques. These methods are time and labor consuming as well as harmful to fish. Therefore, it would be economically important for caviar producing countries to develop accurate, effective and non-invasive method for determination of sex and maturity in sturgeons. Ultrasonography examination was performed to determine sex and differences between matured and immatured Acipenser stellatus. The 249 captured stellate sturgeons larger than 95 cm in length were examined with a linear transducer. Sex determination was carried out based on the differences in echogenicity and morphology of the ovaries and testes. Results of ultrasonography were confirmed at necropsy: 199 fish were female (63 matured and 136 immatured) and 50 were male (29 matured and 21 immatured). Ultrasonographic examination resulted in sex determination with 97.2% accuracy. Gonads of immature males may be difficult to discern. The speed of examination was around 30 seconds or less per fish depending on the stage of maturation of fish.