Rainbow trout are among the most intensively farmed fish species worldwide, and also among those with the most developed understanding of their welfare needs, pain sensitivity, and stress responses.
Trout welfare research has advanced considerably and provides a solid evidence base for improvements. Key stressors include crowding, poor water quality, handling, and transport. Welfare-optimised farms manage water quality continuously, provide adequate space, and use minimal handling techniques. At slaughter, percussive stunning followed by immediate bleeding is the most humane method and is now required in several European jurisdictions. Feeding management is also critical — overfeeding causes digestive stress while underfeeding increases competition. Genetic selection for fast growth in trout has inadvertently created welfare trade-offs including skeletal deformities and immune vulnerabilities, which welfare-focused breeding programmes now try to address.