Responses of growth rates and growth hormone levels of African catfish (Clarias gariepinus) to stocking density
2017
Wang, X.M. | Gao, J.W. | Xu, M. | Mo, B.L. | Dai, W. | Chen, CH.X.
In order to estimate responses of growth rate and growth hormone of Clarias gariepinus to stocking density, fish (initial weight 30.71 ± 0.89 g) were stocked in 120-L tanks at densities of 35, 65, 95, and 125 kg/m^3 for 60 days. On day 30 and 60, the fish growth rates were measured, pituitary growth hormone (GH) mRNA levels and serum GH concentrations were examined by real-time qPCR and ELISA technique, respectively. From day 0 to day 30, there were significant decreases in specific growth rates and relative weight gains at higher densities (95 and 125 kg/m^3) compared to that at lower densities (35 and 65 kg/m^3), whereas no significant effects of stocking density on the two indexes during the day 30−60 were detected. On day 30, GH mRNA levels were unaffected by stocking density, while on day 60, GH mRNA levels were significantly lower at the density of 125 kg/m^3 than in the two lower densities. Serum GH concentration increased with decreasing stocking densities but only significantly between 35 kg/m^3 and the other treatments on day 30. However, there were no significant differences between two lower densities as well as between 65 kg/m^3 and 95 kg/m^3 treatments on day 60. These results implied that effect of stocking density on SGR and RWG of C. gariepinus weren’t uniform in different growth periods and a weak positive correlation was observed between growth rate and GH in C. gariepinus in the present study.
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