DESCRIZIONE
[Problem] Under an underwater environment containing a high concentration of carbon dioxide having an anesthetic effect, prolonged anesthesia is performed on fish and shellfish in a safe and practically simple manner. [Solution Means] Fine bubbles containing gaseous oxygen are brought into contact with the surface of a gill epithelial cell membrane of fish and shellfish to produce a partial pressure difference between [gaseous oxygen partial pressure] - [gill capillary dissolved oxygen partial pressure] exceeding a partial pressure difference between [water dissolved oxygen partial pressure] - [gill capillary dissolved oxygen partial pressure], and thus the amount of oxygen taken by a gill thin plate capillary is remarkably increased. Thereby, respiratory failure which is caused under a spontaneous respiratory movement suppressed by anesthesia is avoided, and thus it is possible to perform prolonged carbon dioxide anesthesia under a water temperature (around 20°C) at which normal fish and shellfish are treated.
[Problem] To safely and practically simply anesthetize fish over a long period of time in an underwater environment which contains a high concentration of carbon dioxide having an anesthetic effect. [Solution] By contacting gaseous oxygen-containing microbubbles with the branchial epithelial cell membrane surface of fish, a difference between partial pressures [(partial pressure of gaseous oxygen) - (partial pressure of oxygen dissolved in branchial capillary vessels)], which is larger than a difference between partial pressures [(partial pressure of oxygen dissolved in water) - (partial pressure of oxygen dissolved in branchial capillary vessels)], is created so that the amount of oxygen taken into branchial plate capillary vessels is remarkably increased. Thus, the fish can be anesthetized with carbon dioxide over a long period of time at a water temperature (about 20°C) commonly employed for handling fishes while avoiding respiratory failure that occurs during spontaneous respiratory movements suppressed by the anesthesia.