Decades of selective breeding in Atlantic salmon aquaculture have dramatically improved growth rates but also introduced welfare trade-offs including increased susceptibility to skeletal deformities and physiological stress.
The genetics of farmed salmon represent a welfare lever with enormous reach: because millions of fish are produced from relatively few genetic lines, breeding decisions affect the welfare of entire generations of farmed salmon at population scale. The historical focus on growth rate as the primary breeding objective created fish that grow impressively but are in some respects less robust — more susceptible to certain diseases, prone to skeletal abnormalities in some lines, and potentially experiencing greater metabolic physiological stress. The shift toward multi-trait breeding objectives that include disease resistance, robustness, and welfare-relevant traits represents a significant positive development. Breeding for sea lice resistance could reduce or eliminate one of the most significant sources of welfare harm in salmon farming. Welfare science informing genetic selection criteria is a promising frontier that could improve the lives of billions of individual fish over coming decades.