Research on tolerance of juvenile Siganus oramin to water temperature, salinity and dissolved oxygen

In order to study the tolerance of juvenile Siganus oramin to cultural environmental factors and provide basic data for the cultivation, we carried out tolerance tests on juvenile S. oramin with body mass (3.25±0.83) g to environment factors such as water temperature, salinity and dissolved oxygen. Besides, we monitored their oxygen consumption rate and respiratory rate under extreme temperature and salinity conditions by hydrostatic respiration chamber methods. The results show that the suitable temperature for juvenile S. oramin ranged from 23.0 to 28.0 ℃, and the tolerance limit temperature ranged from 12.1 to 32.5 ℃; the suitable salinity ranged from 8.0‰ to 59.0‰, and the tolerance limit salinity ranged from 3.5‰ to 75.0‰; the critical point of asphyxiation under normal conditions was (1.47±0.52) mg·L⁻¹. Both temperature and salinity close to the tolerance limit had significant effects on critical point of asphyxiation, asphyxiation point and ultimate hypoxia tolerance of juvenile S. oramin. Low salinity had the greatest effect on critical point of asphyxiation and asphyxiation point, and low temperature had the greatest effect on ultimate hypoxic tolerance value. In conclusion, juvenile S. oramin have a wide range of tolerance to water temperature and salinity, but the oxygen consumption rate and respiration frequency change significantly when they are out of the suitable range, accompanied by strong stress response; juvenile S. oramin have a high asphyxiation point, and are prone to hypoxia, so it is recommended that the dissolved oxygen should be no less than 6 mg·L⁻¹ during the aquaculture process.