| Summary: | Successful management of sturgeon population requires knowledge of stock composition with regard to sex and gonadic stage. Measurement of sex steroid concentration has proven to be a reliable and less invasive method in compare to convention methods. In this study we have examined the possible role of plasma testosterone (T), estradiol (E2), progesterone (P), cortisol (C) and morphometric parameters as indicators of sex and stage of gonadal development in immature (4-5 years old) Great sturgeon cultured in brackish water. Biometry of fishes, blood sampling from caudal vein was performed every three month and plasma was frozen until analyses. Glucose was measured with auto analyser, calcium and magnesium with spectrophotometer and sodium and potassium with film photometer, Hormone levels were measured by radio immunoassay (RIA). Histological preparation was stained with hematoxylin and eosin. In sex determination, result show that total length (L) and weight (W) had no significant elevation in different sexes and can not be used as an indicator sex determination. Among hormones only T had significant elevation, so it could be stated that level of T in immature Great sturgeon could be used to identify sex. In case of gonadic stage result show that total L and W just in male had significant correlation with gonadal stage and among hormones just T in male and C in female had significant correlation. So it could be concluded that in male and female respectively based on T and C measurement gonadic stage in immature Grate sturgeon could be identified. Published
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