Each year, around a trillion fish are caught from the water, primarily for human consumption. A recent study has shed light on the suffering experienced by these aquatic animals during the slaughtering process.
Rainbow trout, originally from cold water tributaries of the Pacific Ocean, are now a popular food fish farmed across the globe. The most common method of killing these fish is through asphyxiation, either in open air or ice water. However, a team of biologists led by Cynthia Schuck-Paim from the Welfare Footprint Institute has revealed that this method can subject each fish to up to 22 minutes of intense pain.
To quantify animal suffering, scientists have developed a standardized framework known as the Welfare Footprint Framework (WFF). This framework takes into account the intensity and duration of negative experiences like stress and pain, allowing professionals working with animals to compare and enhance welfare standards.
The study’s authors emphasize the increasing societal concern for animal welfare in various industries. They believe that by providing quantitative estimates of pain during fish slaughter, significant improvements in animal welfare can be achieved through the adoption of more effective stunning methods.
Through an extensive review of scientific literature, the researchers found that exposure to air for just five seconds triggers a neurochemical response indicative of negative emotions in fish. Behaviors like twisting and turning further demonstrate the animals’ aversion to being out of water.
Without water, fish experience distressing physiological changes, including the sticking together of gill structures that impede oxygen exchange, leading to the accumulation of carbon dioxide. This triggers nociception, the body’s alarm system, causing the fish to gasp for air. Eventually, acidification of the blood and cerebrospinal fluid results in unconsciousness.
Depending on the size of the fish and the slaughtering conditions, these distressing experiences can last between 2 and 25 minutes. The authors estimate that electrical stunning, proposed as a humane alternative, could significantly reduce the duration of pain experienced by fish during slaughter.
While brain scans have shown variations in the effectiveness of electrical stunning, the authors stress the importance of considering the entire harvest process and minimizing pre-slaughter stressors to ensure humane treatment of animals.
By quantifying the pain associated with the most common fish slaughter method, this research provides valuable insights for improving the welfare of billions of animals used for food each year. The study was published in Scientific Reports.
