Effects of water temperature and photoperiod on the oxygen consumption rate of fasted juvenile parrot fish, Oplegnathus fasciatus

Abstract

The effect of water temperature and photoperiod on the oxygen consumption of the fasted juvenile parrot fish, Oplegnathus fasciatus was investigated to provide empirical data for the early-stage culture management and bioenergetic growth model of the species. The mean body weight of the juvenile used for the experiment was 21.5 ± 1.9 g, and the oxygen consumption rate was measured under four water temperatures (10, 15, 20 and 25°C) and three photoperiods (24L:0D, 12L:12D and 0L:24D) with an interval of 5 minutes for 24 hours using a continuous flow-through respirometer. In each treatment three replicates were set up and 15 juveniles were totally involved. The oxygen consumption rates increased with increasing water temperature under all photoperiod treatments (P<0.001). Mean oxygen consumption rates at 10, 15, 20 and 25°C ranged 202.1∼403.4, 306.7∼502.2, 536.7∼791.0 and 879.9≁1,077.4 mg O2 kg-1 h-1, respectively. Q10 values ranged 1.58-2.30 between 10 and 15°C, 2.44∼3.06 between 15 and 20°C and 1.86-2.69 between 20 and 25°C, respectively. Mean oxygen consumption rates of O. fasciatus were the highest in continuous light (24L:0D) followed by 12L:12D and 0L:24D (P<0.001). The oxygen consumption of fish exposed to the 12L:12D photoperiod was significantly higher during the light phase than during the dark phase under all temperature treatments (P<0.001). In summary, oxygen consumption rates of the juvenile parrot fish increase with increasing water temperature and lengthening daylight period; and, thereby, changes in water quality resulted from the depletion of oxygen under high temperature and long daylight photoperiod conditions should be monitored.