Rainbow trout farming produces over 800,000 tonnes annually, with stocking density, water quality, handling practices, and slaughter methods determining welfare outcomes for billions of farmed fish.
Trout aquaculture welfare follows the same fundamental logic as other intensive animal farming: welfare compromises that would be unacceptable in terrestrial vertebrates are routine in fish farming because fish welfare receives less regulatory attention and cultural concern. The evidence base for trout sentience is now substantial - physiological stress responses, behavioral pain indicators, and learning abilities comparable to other vertebrates. Stocking density is the most tractable welfare variable - research consistently shows lower densities produce better welfare outcomes measurable through fin damage, aggression, and stress hormone indicators. Slaughter method reform (electric stunning over CO2 or live-chilling) represents a readily achievable welfare improvement.