Plasma sex steroids and vitellogenin levels in stellate sturgeon (Acipenser stellatus Pallas) during spawning migration in the Danube River

Data are presented on the levels of vitellogenin (VTG) and sex steroids plasma [testosterone (T), estradiol (E2), 11-ketotestosterone (11KT), and 17alpha,20beta-dihydroxy-4-pregnen-3-one (DP)] in stellate sturgeon spawners during their spawning migration in the Danube River. Most sampled fish were 7 years old. Vitellogenesis was still ongoing during the spawning migration. All measured biochemical parameters suggest that spawning will occur by the end of May or later. The VTG values, as well as the ratios E2/T ( discriminating value of 0.002) and E2/11KT ( discriminating value of 0.02), permit differentiation between sexes; the use of these parameters might be applied as a sex identification method for spawners during their spawning migration. The presence of VTG in male plasma indicated a possible exposure to xenobiotic substances in the Black Sea. As a result of high levels of T and 11KT in the females and males during their upstream migration, it is suggested that both of these steroids are involved in stimulating migratory behaviour.