Salmon Farming and Welfare | Animal Welfare Hub

Salmon Farming at Scale

Atlantic salmon (Salmo salar) is the world's most farmed carnivorous fish and one of the most economically important aquaculture species. Norway, Chile, Scotland, Canada, and Australia collectively produce over 2.5 million tonnes of farmed salmon annually, worth approximately $15 billion. The industry keeps hundreds of millions of fish in open-net sea cages, and welfare conditions vary substantially between producers and countries.

2.5M+

Tonnes farmed salmon annually

~500M

Individual salmon harvested per year

Norway

Produces ~50% of global supply

~2yrs

Grow-out period before harvest

Key Welfare Challenges

Sea Lice

Sea lice (Lepeophtheirus salmonis and Caligus spp.) are parasitic copepods that infest farmed salmon in sea cages. Heavy infestations cause significant welfare harm: skin and tissue damage, open wounds, secondary infections, behavioral disruption, and mortality. Sea lice are the single largest welfare challenge in salmon farming.

Scale of Problem: Sea lice infestation is endemic in salmon farms worldwide. Control attempts — using chemical treatments, biological controls (cleaner fish), thermal treatments (warm water), and mechanical delousing — all carry their own welfare costs (stress, injury). The "delousing carousel" — cycles of infestation and treatment — represents a chronic welfare burden throughout the production cycle.

Crowding and Stocking Density

Sea cage stocking densities affect salmon behavior, stress levels, and injury rates. At high densities, subordinate fish show stress indicators, have reduced feeding access, and suffer more fin and scale damage from conspecific aggression.

Research: Studies show salmon kept at lower stocking densities have lower cortisol levels, better growth rates, fewer injuries, and more normal behavioral repertoires. Welfare-optimal densities are substantially lower than commonly used commercial densities.

Slaughter Welfare

Stunning before slaughter is a critical welfare issue for salmon. Traditional methods (CO₂ narcosis, ice slurry) are now recognized as inadequate — salmon remain conscious and stressed during these processes. Better methods exist:

Percussive stunning (a blow to the head) can render fish immediately insensible when properly applied
Electrical stunning systems are available for salmon and produce rapid insensibility
Norway mandates effective stunning before slaughter; Scottish and Norwegian industry leaders have adopted electrical stunning

Progress: Norway's regulations requiring effective pre-slaughter stunning, combined with industry investment in automated electrical stunning equipment, represent the global standard for salmon slaughter welfare. Other producing countries are moving in this direction under industry and regulatory pressure.

Crowding for Harvesting

Before slaughter, salmon are crowded to high densities for pumping and transport — a severely stressful experience. Handling and crowding cause cortisol spikes, physical injury from contact with equipment, and behavioral distress. Minimizing crowding duration and improving equipment design are active welfare improvement areas.

Welfare Standards and Certification

Scheme	Coverage	Welfare Provisions
Norwegian regulatory framework	Norwegian farms (50% of global production)	Mandatory stunning; sea lice limits; stocking density rules
ASC (Aquaculture Stewardship Council)	Global; voluntary certification	Sea lice monitoring; health management; environmental standards
RSPCA Assured (UK)	Scottish farms	Comprehensive welfare standards including stocking density, enrichment, slaughter
Global G.A.P.	Global; mainly European buyers	Basic health and welfare requirements

The Fish Sentience Question

Scientific Consensus Shift: The scientific view on fish sentience has shifted substantially. The 2012 Cambridge Declaration on Consciousness included fish. Research on salmon specifically documents stress responses, avoidance learning, and behavioral indicators of negative states consistent with capacity for suffering. The precautionary case for treating salmon welfare seriously is strong.