- A new study reveals that rainbow trout experience 10 minutes of pain during air asphyxiation.
- Animal welfare advocates criticise air asphyxiation for its duration of pain before fish lose consciousness.
- Air exposure triggers a significant stress response in fish within just 60 seconds, according to the study.
A new study has shown that fish, such as rainbow trout, suffer between two to 20 minutes of intense pain when they are killed for food. The study findings, published in the journal Scientific Reports, focused on a common method of slaughtering fish called air asphyxiation, where fish are deprived of oxygen.
It showed that the rainbow trout endures an average of 10 minutes of moderate to intense pain during air asphyxiation. Animal welfare groups have called out this method, stating that it is an inhumane process given the amount of time it takes them to lose consciousness.
"As little as 60 seconds of air exposure has been shown to elicit a physiological stress response consistently greater than that triggered by longer-lasting stressor," the study highlighted.
"Notably, air exposure is the only stressor capable of causing hydromineral disturbance within such a short time frame. Other stressors (eg, hypoxia, crowding, handling) require longer exposure to elicit comparable responses."
The findings also showed that stuffing fish in ice slurry after catching them could cause even greater pain. During this process, the metabolic process of the fish is slowed down while the lower temperatures extend the time to unconsciousness -- inflicting further misery on these organisms.
The study suggested that electrical stunning, if implemented properly, could significantly reduce the pain experienced by fish -- potentially averting one to 20 hours of moderate to extreme pain for every dollar spent.
"These findings provide transparent, evidence-grounded and comparable metrics to guide cost–benefit decisions and inform slaughter regulation," it stated.
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The researchers hope that the findings could help improve the welfare of up to 2.2 trillion wild and 171 billion farmed fish killed every year for human consumption.
"The Welfare Footprint Framework provides a rigorous and transparent evidence-based approach to measuring animal welfare and enables informed decisions about where to allocate resources for the greatest impact," said Wladimir Alonso, a co-author of the study.
"These findings provide transparent, evidence-grounded and comparable metrics to guide cost-benefit decisions and inform slaughter regulations and practices in trout."
