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Respiratory response of grass carp Ctenopharyngodon idellus to dissolved oxygen changes at three acclimation temperatures
- Zhao, Zhigang, Dong, Shuanglin, Xu, Qiyou
- Fish physiology and biochemistry 2018 v.44 no.1 pp. 63-71
- Ctenopharyngodon idella, acclimation, dissolved oxygen, fish, hypoxia, normoxia, oxygen, oxygen consumption, respiratory rate, temperature
- Respiratory parameters of grass carp were studied during dissolved oxygen (DO) changes from normal DO to hypoxia, then return to normal DO at 15, 25, and 30 °C acclimation, respectively. The results showed that with increases of acclimation temperature at normoxia the respiratory frequency (fR), oxygen consumption rate (VO₂), respiratory stroke volume (VS.R), gill ventilation (VG), and VG/VO₂ of grass carp increased significantly, but the oxygen extraction efficiency (EO₂) of fish decreased significantly (P < 0.05). With declines of DO levels, the fR, VS.R, VG, and VG/VO₂ of fish increased significantly at different acclimation temperatures (P < 0.05). A slight increase was found in VO₂, and the EO₂ of fish remained almost constant above DO levels of 3.09, 2.91, and 2.54 mg l⁻¹ at 15, 25, and 30 °C, while the VO₂ and EO₂ began to decrease significantly with further reductions in DO levels (P < 0.05). After 0.5 h of recovery to normoxia from hypoxia at three acclimation, the fR, VS.R, VG, and VG/VO₂ of the fish decreased sharply; meanwhile, the VO₂ and EO₂ increased sharply (P < 0.05). The respiratory parameters of fish gradually approached initial values with prolonged recovery time to normoxia, and reached their initial values in 2.5 h at 25 and 30 °C acclimation. The critical oxygen concentrations (Cc) of fish for VO₂ were 2.42 mg l⁻¹ at 15 °C, 2.02 mg l⁻¹ at 25 °C, and 1.84 mg l⁻¹ at 30 °C, respectively. The results suggest that grass carp are highly adapted to varied DO and short-term hypoxia environments.