Rainbow trout is the UK's primary farmed freshwater fish. Welfare research on trout is more advanced than for many other farmed species, providing a basis for evidence-based improvements in farming systems.
Rainbow trout welfare science is well-developed compared to other farmed fish species. Research demonstrates that trout learn to avoid painful stimuli, show behavioural changes in response to injury, and produce stress hormones in response to poor welfare conditions. Fin damage — used as a key welfare indicator — increases significantly at high stocking densities. Pre-slaughter crowding, out-of-water handling and CO2 stunning all produce measurable welfare costs. Percussive stunning (blow to the head) or electrical stunning followed by immediate bleeding represents best welfare practice at slaughter. Farms that monitor fin condition as a routine welfare audit and adjust stocking to maintain fin integrity produce both better welfare outcomes and better flesh quality.