Abstract:Studies on the oxygen consumption rate, its diurnal variation and asphyxiation point of rock bream Oplegnathus fasciatus at different salinities (20, 25, 30) and temperatures (15℃, 20℃, 25℃) were carried out in Qingdao Zhonghai Fishery Corporation, Ltd. from April to August, 2008. The experimental fish were divided into two groups: 70d-old group at an average body weight of 1.07g and an average body length of 37.68 mm; 105d-old group at an average body weight of 5.59g and an average body length of 65.71 mm. The results showed that relative oxygen consumption rate of 105d-old fish was significantly higher than that of 70d-old fish, while the asphyxiation point of the former was lower. The oxygen consumption rate of rock bream decreased as their body weight increase. Both relative oxygen consumption rate and individual oxygen consumption increased with the rise of water temperature when salinity was unchanged. The effect of salinity on oxygen consumption rate of 70d old fish was significant (P＜0.05) whereas it was not significant for 105d-old fish (P＞0.05). The optimum salinity for growth of rock bream was 25, and the optimum temperatures were 20～25 ℃. The asphyxiation point of rock bream were between 1.602 1 mg O2/L and 2.953 8 mg O2/L at different temperatures and salinities and it decreased with the increase in body weight. Neither salinity nor temperature had significant effects on which (P＞0.05). The oxygen consumption rate of the young fish was 0.945 9 mg O2/g.h in daytime, which was about 3-5 times higher than the nighttime. Rock bream showed high metabolism rate till 22∶00pm.
