Seasonal fluctuations of steroid hormones in beluga sturgeon Huso huso cultured in brackish water

Abstract

The experiment was carried out in one year on blood sexual hormones in 74 four-years old beluga sturgeon Huso huso held in 8 round cement tanks in brackish water with salinity of about 13.5 ppt. Fishes were biopsied at the beginning of the experiment in order to determine the sexuality and gonadic stage. Blood sampling was performed in caudal veins three times during experiment in fall, winter and spring seasons.Testosterone (T), Esteradiol (E2) and Progesterone (P) were measured by Radio Immune Assay (RIA) method. Test of profile was done in duplicate. Statistical results showed a significant elevation (p < /em> > 0.05) on measured factors in both sexes, especially in males.In males, testosterone (T) depends on gonadic stage had significant elevation; but in females, there was no significant increase (p < /em> > 0.05) in estradiol (E2) and progesterone (P) which probably resulted from their ages. In males, T level in stages II, II-III, III, IV, were 5.5, 4.4, 6.3, 2.6 ng/ml, respectively.The result indicated that the amount of T increased by development of gonads until III stage, then suddenly decreased in stage IV. Quantities of P and E2 were measured only in females.Amounts of P and E2 in stages of II, II-III, were 0.12, 0.13 and 1.455, 0.81 ng/ml, respectively, suggesting the increase of P and decrease of E2 were associated with gonad progress. According to the results, it was demonstrated that sexual hormones were affected by season, environmental conditions and gonadal stages.Therefore, inland underground brackish water as a new medium culture was effective in reduction maturity time in beluga.