Trout farming is one of the most established freshwater aquaculture sectors, but welfare standards lag behind what is achievable given current knowledge of fish pain and stress physiology.
Rainbow trout are intelligent, fast-moving fish adapted to cold, oxygenated streams. High-density aquaculture environments restrict movement, increase aggression, and compromise water quality in ways that cause measurable physiological stress. Slaughter by asphyxiation in ice water — common in smaller operations — is the least humane method available and can take minutes to cause unconsciousness. The technology for better practice exists: recirculating aquaculture systems, lower densities, and electrical or percussion stunning are all commercially viable and increasingly required by leading certification schemes.