Atlantic salmon in sea cage culture during the primary growth phase face welfare challenges from sea lice, disease, crowding, and handling stress.
Sea cage salmon welfare during the growth phase is dominated by the sea lice problem. Treatments applied to control lice — chemicals, thermal, mechanical — all cause welfare harms of varying severity. The cycle of infestation, treatment, reinfestation is relentless in open sea cage systems, creating chronic stress across the production cycle. Closed containment systems eliminate sea lice entirely by removing the connection between the farm and the wild environment, but require larger capital investment. The transition to closed containment or land-based aquaculture is the most promising welfare solution for salmon farming, though it is progressing slowly against economic inertia.