Fish out of water feel intense pain for 10 minutes

Ten minutes of intense pain : this is how much a trout suffers when it is pulled out of the water and left to die of asphyxiation , according to a common practice in many fish farms. This is indicated by a study published in the journal Scientific Reports by an international team of biologists led by Cynthia Schuck-Paim of the US research organization Welfare Footprint Institute. The researchers took into consideration the rainbow trout (Oncorhynchus mykiss), a fish native to the Pacific Ocean but now farmed on every continent except Antarctica. Most of the time , these animals are left to die of asphyxiation , in the open air or in icy water . Quantifying the suffering caused by this practice is complicated , but a standardized method (Welfare Footprint Framework) has recently been developed that takes into account the intensity of negative states such as stress or pain and the duration of their experience. Using the tool, researchers combed through a wealth of published scientific papers on the topic, building a detailed picture of a fish out of water experience . The data show that just five seconds of exposure to air triggers a neurochemical response that is associated with negative emotions in humans. Behaviors such as writhing and twisting further demonstrate the fish's intense aversion response . Without water , the delicate gill structures that exchange oxygen for carbon dioxide stick together , causing a buildup of CO2 from breathing. These rising levels trigger pain perception , the body's alarm system, which causes the fish to gasp. Finally, the elevated CO2 levels acidify the animal's blood and cerebrospinal fluid , eventually causing it to lose consciousness . Electrical stunning, proposed as an alternative for killing fish, could save minutes of suffering. However, brain scans have shown that effectiveness can vary greatly: ideally the animal should be rendered completely unconscious immediately until death, but with current stunning methods this is not always possible.