A new study in Scientific Reports reveals the hidden pain of fish during slaughter and offers practical solutions to improve their welfare. Focusing on rainbow trout, the research quantifies pain in air asphyxia—a common slaughter method—using the innovative Welfare Footprint Framework (WFF). With up to 2.2 trillion wild and 171 billion farmed fish killed annually, the findings highlight an opportunity for welfare reforms on a massive scale.

The study shows rainbow trout endure an average of 10 minutes of intense pain during air asphyxia, with estimates ranging from 2 to 22 minutes depending on factors like fish size and water temperature. This translates to approximately 24 minutes of pain per kilogram of fish. These estimates are based on a comprehensive review of existing research to assess the intensity and duration of pain and distress experienced by the fish.

Crucially, the study also assesses the cost-effectiveness of interventions. If implemented properly, electrical stunning could avert 60 to 1,200 minutes of moderate to extreme pain for every U.S. dollar of capital cost.