Rainbow trout is one of the most widely farmed fish species in temperate regions, with welfare challenges from crowding, water quality, and aggressive social interactions.
Rainbow trout welfare is an important and relatively neglected field given the large scale of global production. Trout are active, territorial fish that experience significant stress from crowding and social competition. Dominant fish within pens have access to better food and oxygenated water while subordinates suffer from both aggression and resource competition. Temperature extremes during summer in many regions push trout beyond their thermal comfort range. Developing species-appropriate welfare standards for trout requires both more research and stronger regulatory attention.