Rainbow and brown trout farming faces significant disease challenges including whirling disease, bacterial gill disease, and furunculosis, with welfare implications for millions of farmed fish.
Trout disease welfare reflects the high sensitivity of this species to environmental and pathogenic stressors. Bacterial gill disease causes progressive respiratory compromise that is directly welfare-relevant - fish struggling to extract oxygen from water through damaged gill tissue experience distress analogous to breathing difficulty. Whirling disease creates permanent neurological damage causing disorientation and inability to feed normally - a chronic welfare condition for surviving fish. The limited therapeutic options available for trout compared to salmon mean that prevention through excellent water quality management is especially critical. Farms with consistent water temperature control, adequate oxygen, and low stocking density demonstrate dramatically lower disease incidence and better welfare outcomes.