Short-period fluctuations in ambient temperature have a major impact on the growth and energy metabolism of fish.Under indoor controlled conditions,the growth and energy distribution of the brown flounder(Paralichthys olivaceus)juveniles undergoing the cycles of high temperatureoptimal temperature operation were investigated.During a single10day cycle,the 20 ℃ acclimated juvenile brown flounder were cultured at high temperature(26.5 ℃)for different days as follows:0 d(H₀),2 d(H₂),4 d(H₄),6 d(H₆),and 8 d(H₈),and then maintained at 20 ℃(optimal temperature)for the remaining days.The fish were stocked in five recirculating systems and each system was equipped with three aquaria(80 cm×50 cm×35 cm,about 140 L).Aeration was continually provided to keep the dissolved oxygen content above 5.5 mg/L.The salinity of the seawater was 30 and pH was 7.5±0.3.A photoperiod of 14 L∶10 D was adopted during the experiment.The fish were cultured for 4 cycles(40 d)and at the end of the experiment period,the body weight of fish which experienced different periods of high temperature exposure expressed in dry mass,wet mass,protein,and energy were all significantly lower than those of control group(H₀).The lipid contents of the final fish which experienced high temperature were significantly higher than those of H₀.Similar trend was observed in the protein contents of the final fish,except that H₆ was slightly lower than H₀.Through the experimental period,less feed ingestion and smaller fraction of energy allocated to growth mainly depressed the growth of fish which experienced different periods of high temperature exposure.The feed ingestion of the fish which experienced different periods of high temperature exposure was slightly lower than that of the controls,but the feeding rate,digestibility and food conversion efficiency were not significantly different from those of the control group.The energy allocated to growth in H₂, H₄,and H₆ was not significantly different from H₀.The highest proportion of energy lost in feces and excretion appeared in H₄ and H₆ respectively.The energy distribution in the growth in H₈ was significantly lower than other treatments and its proportion of metabolic energy consumption was significantly higher than other treatments.The daily unit body weight energy ingestion of the fish which experienced different periods of high temperature exposure were was significantly different from H₀,but the energy allocated to growth was significantly lower than that of H₀.It could be concluded that the complete and over compensatory growth can not be achieved in similar highoptimal temperature operation.The above results indicated that the juvenile brown flounder showed poor flexibility to the cycle of hightemperatureoptimumtemperature operation and temperature fluctuation would impact their growth.