The influence of water temperature and ration on the growth, body composition and energy budget of tongue sole (Cynoglossus semilaevis)

The influence of water temperatures (16, 22 and 28 °C) and ration levels (0%, 25%, 50%, 75% and 100% of satiation) on the growth, body composition and energy budget in juvenile tongue sole (Cynoglossus semilaevis) was investigated over 60 days. The specific growth rates of fish increased with increasing ration levels. Fish fed to 100% satiation at 22 °C exhibited better growth than other treatments. The relationship among SGRw, SGRe, temperature (T) and ration (RLw, in weight and RLe, in energy) could be described by the regression equations: SGRw = 20.778 log(RLw + 5) − 0.0767T − 13.628, SGRe = 11.016 log(RLe + 5) − 0.152T − 6.730. The maintenance ration levels were 0.19%, 0.46% and 0.74% of body weight, while 1.79%, 3.21% and 4.94% of body energy at 16, 22 and 28 °C, respectively. Ration level from 50% to 100% satiation did not influence food conversion efficiency. There is no significant difference in apparent digestion rate between fish fed to 75% and 100% satiation. The content of lipid in fish tended to increase with increasing ration levels, while tended to decrease with increasing water temperature. The crude protein content in fish tended to decrease with increasing ration levels at low temperature (16 °C), while tended to increase at high temperature (22 and 28 °C). The proportion of food energy assimilated in growth and the proportion consumed for respiration dominated the mode of the energy allocation of juvenile tongue sole. In the temperature range of this experiment, the proportion of food energy allocated to growth decreased with increasing temperature, and was not affected significantly by ration level from 50% to 100% satiation at the same temperature. The proportion of food energy consumed for respiration decreased with increasing ration, while increased with increasing temperature. The maximum specific growth rate occurred in fish fed to satiation at 22 °C, which suggested that commercial farmers could feed juvenile tongue sole to satiation at 22 °C to obtain higher growth rate.