Cooling combined with hyperoxic CO2 anesthesia is effective in improving the air exposure duration of tilapia

Abstract

Tilapia were subjected to cooling (CO, a stepwise reduction in temperature from 30 °C to 15 °C), anesthesia (AN, anesthetized by hyperoxic carbon dioxide), air exposure (AE, exposed to air) and cold tolerance (CT, in 15 °C water) treatments, and the physiological responses were determined after the treatments. CO followed by AN treatment for tilapia could meet the criteria of an ideal anesthetic. Fish were deeply sedated within 69 s, completely anesthetized within 276 s and recovered within 308 s without any mortality. The stress responses induced by the CO&AN treatment were mild, whereas they were consistently increased in the AE treatment. Furthermore, the AE treatment caused tissue damage. The AE duration was significantly improved by CO&AN treatment, and the survival time of the CO&AE, AN&AE and CO&AN&AE treatments were 313 min, 351 min and 561 min, respectively, in the laboratory experiments, whereas the survival rate of the CO&AN&AE treatment group after 240-min air exposure was 95.2% in the pilot test. It appeared that cooling followed by hyperoxic CO2 anesthesia would be suitable for handling tilapia in a short-time air exposure procedure.

The Influence of Hypothermia Hibernation Combined with CO2 Anesthesia on Life and Storage Quality of Large Yellow Croaker (Pseudosciaena crocea)

“…The increase in RBC directly induced an elevation in HCT. The stress response did not disappear immediately after the fish recovered, consistent with the prior observations of strong stress responses in fish 30 min after recovery, with the subsequent return to basal values of stress response indicators, such as HCT and cortisol, within 90 min [ 14 , 26 ]. However, the changes in MCH before and during hibernation and after recovery were not significantly different, indicating that the combined method of hypothermia hibernation and CO 2 anesthesia for the large yellow croaker did not influence the hemoglobin transport function.…”

“…This rapidly decreased to 58.33% for 2.5 h when the aeration rate increased to 7.0 ppm/s. This may be because the rapid increase in CO 2 concentrations inhibited the loading of oxygen on red blood cells, resulting in hypoxic respiratory failure [ 10 , 14 ]. Our results suggested that the aeration rate of CO 2 at 2.0 ppm/s was the optimal anesthesia condition for the large yellow croaker.…”

“…The recovered fish took an average of 18.5 ± 4.9 min to resume an upright equilibrium and swimming motion. When the fish were treated with CO 2 , the concentration of CO 2 in their blood increased, causing changes in blood indicators, CO 2 concentration in the blood, and their influence could last as long as 180 min despite the fish waking [ 12 , 14 ]. The cooling of live fish involved a process of temperature acclimation [ 25 ]; CO 2 anesthesia could reduce the metabolism of the fish to compensate for the physiological changes due to stress caused by temperature changes.…”

“…The LYM and HCT are recognized as useful indicators for measuring stress response during anesthesia and cryopreservation. Their increase is synchronous with the rise in cortisol, which is primarily associated with metabolic shifts in accordance with escape responses [ 14 , 23 ]. The LYM and HCT results indicated that the large yellow croakers experienced stress during hibernation, which persisted after recovery.…”

“…Alternatively, carbon dioxide (CO 2 ) dissolved in water is an effective anesthetic in various aquatic animals [ 10 ], and is ideal for creatures intended for human consumption, since no toxic substances remain in the organisms [ 11 , 12 ]. However, CO 2 is only suitable for short-term anesthesia, and prolonged CO 2 anesthesia is likely to induce death due to respiratory failure [ 13 , 14 ]. The development of a new green method utilizing hypothermia hibernation with CO 2 rapid hypnosis for the long-term transportation of marine fish is worth investigating using the live large yellow croaker as a model.…”