Growth compensation in juvenile tongue sole,Cynoglossus semilaevis(Güther, 1873): responses to thermal stress and feed restriction

Abstract

Responses of compensatory growth to high temperature and feed restriction in juvenile tongue sole, Cynoglossus semilaevis (Guther, 1873), were investigated during a 56-days experiment. Fish were divided into seven groups including three high-temperature treatments which were reared at 28°C for 1, 2 and 3 weeks, respectively, then returned to 22°C (recorded as T1, T2 and T3), three feed-restricted treatments which were fed 25% satiation for 1, 2 and 3 weeks, respectively, then fed ad libitum (recorded as R1, R2 and R3) and a control (continuously reared at 22°C). The results showed that juvenile tongue sole exposed to thermal stress for 1 week exhibited overcompensatory growth. However, complete compensation occurred in T2, T3 and R1 fish, while partial compensation occurred in R2 and R3 fish. The body composition and energy content of fish were not significantly different among all treatments (P > 0.05). The specific growth rate and feed efficiency of fish in T1 were significantly higher than other treatments during the whole experiment period (P < 0.05). Higher feed efficiency and apparent digestion rate during recovery might account for the compensatory growth in tongue sole in the present study. Hyperphagia played an important role in compensatory growth for feed-restricted fish, but was not involved in the compensatory response in thermal stressed fish in the present study. The results from the present study suggested that a suitable thermal stress could be more feasible to elicit compensatory growth than feed restriction in juvenile tongue sole.