Atlantic cod (Gadus morhua) have been farmed experimentally and commercially since the 1990s, primarily in Norway, Scotland, and Iceland. Despite challenges with reproductive management, cod aquaculture offers an alternative to wild capture of a historically over-exploited species.
Atlantic cod are large, active, cannibalistic gadoids capable of reaching 20kg+ in wild conditions. They are highly social, forming aggregations and showing complex social hierarchies. Their visual system is adapted for active predation. The species has well-characterised stress responses and shows clear avoidance learning in experimental contexts. As with other teleost fish, the evidence base for nociception and potential pain experience is substantial.
Cannibalism: Cod are aggressive cannibals, particularly at high stocking densities or during irregular feeding. Size-grading to reduce size heterogeneity within tanks significantly reduces cannibalism-related injuries and mortality. Underfeeding dramatically increases cannibalism; maintaining ad libitum feeding regimes is essential for welfare.
Stocking density: Optimal stocking densities for cod welfare are lower than for salmonids — 15–25 kg/m³ is recommended. Higher densities increase aggression, fin damage, and chronic stress.
Maturation and reproductive cycling: Cod mature early in captivity and undergo significant physiological changes associated with spawning. Photoperiod manipulation prevents premature maturation (which causes welfare problems and production losses) and manages reproductive timing. However, photoperiod manipulation itself represents an interference with natural biology that may have welfare implications.
Spinal deformities: Cod show relatively high prevalence of skeletal deformities including spinal curvature in farmed conditions. Deformities cause long-term welfare compromise and are associated with nutrition, water quality, and genetic factors.
Cod are visual surface feeders, detecting prey by sight and movement. Dry pellet acceptance requires conditioning but is achievable. Irregular or insufficient feeding causes aggressive competition, increased cannibalism, and stress-related immune suppression. Automated feeding systems with waste pellet detection optimise feeding efficiency and reduce both welfare problems from underfeeding and water quality problems from overfeeding.
Vibriosis, furunculosis, and parasitic infections are significant in cod aquaculture. Vaccination programmes are available and effective. Sea lice from co-located salmon farms present a biosecurity challenge. Disease outbreaks in cod are associated with stress periods, suggesting that welfare improvements (reduced density, better feeding) simultaneously improve disease resistance.
Electrical stunning provides rapid loss of consciousness for cod slaughter. Percussion stunning and CO₂ are also used. As with all farmed fish, the goal is immediate unconsciousness before any noxious procedure. RSPCA Assured and GlobalG.A.P. standards specify stunning requirements for cod.
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