Rainbow trout are one of the most studied farmed fish for welfare, yet significant challenges remain around stocking density, feed management, and pre-slaughter handling.
Rainbow trout welfare is better researched than most farmed fish species, partly because of their use as laboratory models. This research confirms they experience pain, fear, and stress through mechanisms similar to other vertebrates. Commercial production at high stocking densities causes chronic crowding stress, fin damage from aggression and abrasion, and in some systems, chronic exposure to elevated water temperatures. Flow-through systems depend on clean river water and are vulnerable to source water quality changes; RAS provides more control but involves higher densities. Pre-slaughter crowding causes acute stress that can be measured through cortisol elevation and behavioral indicators. Electrical stunning is the most humane available method but adoption across the industry is incomplete. RSPCA Assured and similar schemes set meaningful welfare standards for trout production.