Papers by Author: Han Wen Yuan

Abstract: This study investigated the effects of busulfan on sex reversal in the Asian swamp eel (Monopterus albus) by evaluating the estradiol (E2) and testosterone (T) concentrations, gonadosomatic index (GSI) and sex ratio. Fish (9.80 ± 1.07 g average initial weight; n = 3 per group) were fed with five diets containing 0 (control), 10, 30, 50 or 70 mg kg-1 dietary busulfan concentrations to apparent satiation for 15 months. Serum E2 and T concentrations were determined by radioimmunoassay techniques. Both E2 and T concentrations were significantly affected by busulfan, while there were no significant differences among the treated groups. Serum E2 concentrations and GSIs decreased, while T concentrations increased with increasing busulfan levels in each group. A shift in the sex ratio towards more male and intersex fish was observed with increasing busulfan contents. The highest male ratio obtained in the 70 mg kg-1 group was significantly different compared to the other groups. High doses of busulfan may induce deformed individuals and high mortality in M. albus. Therefore, busulfan may inhibit gonad development and promote the sex change from female to male M. albus.

Abstract: This study investigated the effects of exogenous estradiol on sex reversal in the Asian swamp eel (Monopterus albus) by evaluating the estradiol (E2) and testosterone (T) concentrations, gonadosomatic index (GSI), hepaticosomatic index (HSI) and the sex ratio. Fish (9.60 ± 0.92 g average initial weight; n = 3 per group) were fed with six different diets containing 0 (control), 20, 40, 60, 80 or 100 mg kg-1 dietary estradiol contents to apparent satiation for 15 months. Serum E2 and T concentrations were determined by radioimmunoassay. Levels of E2, GSI and HSI significantly increased while T concentrations and survival rates decreased as the exogenous estradiol levels were raised. Sex ratios did not differ significantly among all exogenous estradiol treatments, and there were no significant differences between the control group and the 20 mg kg-1 treatment group. Therefore, exogenous estradiol can maintain the female activity and delay sex reversal in M. albus. This study provides important information for successful reproductive management and may be exploited for the aquaculture of this species.

Abstract: The aim of this study was to investigate the effects of exogenous melatonin on sex reversal in the rice eel (Monopterus albus). This was carried out by evaluating the estradiol (E2) and testosterone (T) concentrations, gonadosomatic index (GSI) and sex ratio. Fish (9.80 ± 1.20 g average initial weight; n = 3 per group) were fed with one of five practical diets containing 0 (control), 10, 30, 50 or 70 mg kg-1 dietary melatonin contents to apparent satiation for fifteen months. Serum E2 and T concentrations were determined by radio immunoassays. E2 and T concentrations, GSIs and survival rates significantly decreased with increased concentrations of exogenous melatonin. Fish fed 70 mg kg-1 of dietary melatonin showed significantly lower rates of E2, T, GSIs and survival ratio than those fed with lower melatonin concentrations or the control group. The shift of sex ratio towards more male and intersex fish was correlated with increasing dietary melatonin contents. Therefore, a high dosage of melatonin may inhibit gonadal development and promote sex change from female to male in M. albus.

Abstract: The effects of stocking density on various growth parameters and sex reversal in the rice field eel (Monopterus albus) were investigated by evaluating steroid hormone, the gonadosomatic index (GSI) and sex ratio. Fish (mean initial weight of 9.88 ± 0.70 g) were stocked to densities of 4, 20, 36, 52, 68, 84 or 100 fish/m2 in cages (2 m × 1 m × 1.5 m) in a pond, with five replicate cages for each density. Fish were fed for 420 days on a formulated isocaloric diet containing 40.22% crude protein and 12.86 MJ/kg. Serum E2 and T concentrations were determined by radioimmunoassays. There were no significant differences in final bodyweight (FBW) and daily weight gain (DWG) for fish in the groups containing less than 52 fish/m2, while FBW and DWG were significant lower in groups at 68 fish/m2 or more. Specific growth rate (SGR) differed significantly between the 84 and 100 fish/m2 groups compared with the 4, 20 and 36 fish/m2 groups. There was no significant difference in SGR in groups containing less than 84 fish/m2. There were no significant difference between the 4 and 20 fish/m2 groups in net yield (NY), but these groups did differ significantly from the other groups. The final condition factors of fish stocked at 84 or 100 fish/m2 were significantly lower than fish stocked at the other densities. E2 and T hormone concentrations declined as stocking density increased, while GSI values increased initially but then reduced with increasing stocking density. Female ratio and survival decreased with increasing stocking density. The proportion of male fish was significantly greater in the three highest stocking density groups. Therefore, high stocking density may promote sex change from female to male in M. albus.