Rainbow trout are the most farmed freshwater fish in the UK, with welfare considerations spanning stocking density, water quality, handling and slaughter methods.
Crowding during harvest increases cortisol and reduces welfare in the hours before slaughter. Asphyxiation in air or ice slurry is slow and distressing — percussive stunning kills trout instantly. Water quality management — oxygen, ammonia, temperature — directly determines chronic welfare outcomes in intensive systems. UK certification schemes are among the most advanced for farmed fish welfare, with RSPCA Assured standards setting benchmarks for stocking density, stunning and handling.