Gender identification in great sturgeon (Huso huso) using morphology, sex steroids, histology and endoscopy.

Gender identification of great sturgeon during different life stages was conducted using morphology, sex steroid concentrations, histological and endoscopic techniques. One hundred and forty great sturgeons from two sturgeon farms at ages between 3-16 years were selected for examination. Most of the morphological indices showed no significant sex-related differences except for the ratio of fork length to distance of snout to anterior of dorsal fin (PD). The urogenital opening had no difference in shapes for both sexes. Mean sex steroid concentrations showed no significant difference in levels of testosterone, estradiol and progesterone between males and females in the stage II of maturity. 95.8% of fish were correctly sexed using endoscopy at this stage. Histological investigation indicated the ovaries of 3- to 9-year-old females were at the different stages of pre-vitellogenic, and most males were at the early spermatogenesis for age 3. The result of this study suggests that endoscopy is a reliable tool for sex and stage determination after the age of 3 years. This method is useful in providing a quick discernment of sexes and stages compared with utilizing morphometric and blood indices. Direct observation of gonads can give us important information about the gonadal and maturity stages in sturgeon aquaculture and wild population management, with minimal damage or stress to this endangered species.