Egg quality and plasma testosterone (T) and estradiol-17β (E2) in white sturgeon (Acipenser transmontanus) farmed for caviar

Field trials were conducted at two sturgeon farms to test the hypothesis that husbandry and dietary regimes affect egg quality, caviar yield, plasma sex steroids and the incidence of ovarian atresia in white sturgeon (Acipenser transmontanus) farmed for caviar. Ninety-two females from the same year-class were fed two different commercial diets at each of two farms for 6 months, followed by a 5 month 'vernalization' period at a communal cold water facility where the same dietary treatments were applied. Individually marked fish were sampled before and after vernalization for length, weight, plasma T and E-2. At harvest, marked fish were sampled for caviar yield and egg texture, size, and polarization index. A factorial fixed model did not reveal any significant effects of farm and diet on caviar yield or egg qualities (P > 0.05). A mixed model with repeated measure revealed an effect of farm on plasma T concentrations (P < 0.001) and a significant decrease in plasma T level after vernalization (P < 0.001). The plasma E-2 concentrations increased after vernalization (P < 0.001) but at a different rate in the two farm stocks (P = 0.009). Fish from both farms lost 2.7 +/- 0.96 kg, or 6% of their body weight, and their condition factor (Fulton) decreased after vernalization (P < 0.001). Histological analysis of sturgeon eggs at harvest revealed signs of follicular atresia in only one female.