Rainbow trout is one of the most widely farmed fish globally. Their welfare in different production systems reveals how system design profoundly affects fish welfare outcomes.
Trout welfare in aquaculture varies substantially with system design and management. High-density stocking in any system causes competition for space and resources, leading to fin-biting, injury, and chronic stress. Water quality parameters critical to trout welfare including oxygen, temperature, and ammonia are easier to maintain in well-managed flow-through and recirculation systems than in static pond systems. Predator presence at outdoor farms causes sustained fear responses that are measurable through cortisol and behaviour changes. Slaughter welfare for trout is an area where improvement is practical and impactful: percussive stunning achieves immediate insensibility while bleeding without prior stunning allows extended consciousness during blood loss. The welfare gains from adopting humane slaughter methods are accessible with modest investment.