Determination of sex and maturity in Acipenser stellatus by using ultrasonography

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 ۲۴۹ captured stellate sturgeons larger than ۹۵ 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: ۱۹۹ fish were female (۶۳ matured and ۱۳۶ immatured) and ۵۰ were male (۲۹ matured and ۲۱ immatured). Ultrasonographic examination resulted in sex determination with ۹۷.۲% accuracy. Gonads of immature males may be difficult to discern. The speed of examination was around ۳۰ seconds or less per fish depending on the stage of maturation of fish.

Keywords:

Stellate sturgeon , Acipenser stellatus , Ultrasonography , Sex determination immature gonads , Mature gonads