Rainbow Trout Feel Pain and Suffer for Minutes After Being Caught, Study Finds

In a new study, scientists have quantified the amount of pain and suffering fish, specifically rainbow trout (Oncorhynchus mykiss), feel when they are caught and left in the open air prior to slaughter.

According to the study, published in the journal Scientific Reports, the fish experience around 10 minutes of moderate to intense pain during air asphyxia. After being caught by fishing hooks or nets, fish are pulled from their aquatic habitat. From the moment they reach the open air and as they remain alive onboard a boat, they experience painful suffering for around 2 to 21 minutes.

The quantified pain can also be determined by weight, with scientists finding that fish suffer for about 24 minutes per kilogram of weight. In some instances, fish could experience over one hour per kilogram of hurtful, disabling, or excruciating pain, the study authors wrote.

As Earth.com reported, chilling fish on ice only prolongs the suffering for the trout, which are adapted to cooler waters. This practice can also lead to thermal shock and tissue damage, worsening the pain.

According to the study, over 1 trillion fish are slaughtered each year, and rainbow trout are one of the most commonly slaughtered fish. The fish experience many levels of trauma and suffering before they are ultimately slaughtered, and the study authors want to emphasize more humane methods of capturing fish for food.

Welfare Footprint Institute, with which several of the study authors are affiliated, reported that fish can suffer through many different processes leading up to slaughter, including a fasting period to empty their guts; stress from crowding; physical pain from nets, rough handling and air exposure; stress from transportation; and more.

As an alternative, the study authors have recommended using stunning methods to prevent fish from feeling pain when captured for slaughter. These practices, either by electrical or percussive stunning, could cost about 6 cents per kilogram of trout, but the impact could avoid between one and 20 hours of moderate to extreme pain for every dollar invested. 

However, other practices during capture and transport would also need to be amended to reduce stressors and make fishing more humane, the authors suggested.

While the study investigated suffering for rainbow trout, the authors explained that the identified patterns are likely similar for other fish captured for slaughter, such as salmon or tilapia. More research is needed to quantify specific pain amounts for other species, but the study results could still serve as a baseline, the authors explained.

“These findings have immediate relevance for shaping slaughter standards and can inform decisions that must balance animal welfare, economic and environmental considerations,” the authors concluded. “Ultimately, this approach may facilitate more evidenced-informed collaboration across disciplines, paramount to improve the lives of animals on a large scale.”