Long-term effects of intraperitoneal injection of estradiol-17β on the growth and physiology of juvenile stellate sturgeon Acipenser stellatus

Juvenile stellate sturgeon Acipenser stellatus were intraperitoneally injected with estradiol-17 beta (E-2; 0 and 5 mg/kg fish) to investigate the possibility of sex reversal and also determine the changes in biochemical parameters. Five-month-old fish (40.9 +/- A 1.1 g) were injected every 3-week interval during a 190-day trial. At the termination of the experiment, final weight and other growth parameters including weight gain and specific growth rate, hepatosomatic and viscerosomatic indices were not affected by repetitive injection of E-2. Hematological features of E-2-treated fish showed significant reductions in number of red blood cells, hemoglobin concentration, hematocrit value and mean corpuscular hemoglobin (P < 0.05), but no significant changes were observed in number of white blood cells, mean corpuscular volume and mean corpuscular hemoglobin concentration (P > 0.05). Calcium, phosphorus, glucose, triacylglycerol, cholesterol, total protein and estradiol concentrations were significantly increased in fish injected with E-2 (P < 0.001). Plasma progesterone and testosterone levels were noticeably lower in fish injected with 5 mg/kg E-2 rather than the control fish (P < 0.001). Histological observations of gonads showed that all fish injected with 5 mg/kg E-2 apparently feminized, while 66.6 % of the control group was female. These results revealed that the injection of E-2 is an effective method for feminization of stellate sturgeon without having significant inhibitory effects on growth and survival.