Stocking density is one of the most welfare-critical variables in fish farming — high density causes aggression, injury, disease, and chronic stress.
Stocking density is a primary driver of welfare outcomes in commercial fish farming. At high densities, fish cannot avoid aggressive conspecifics, water quality deteriorates more rapidly, stress hormones are chronically elevated, and disease transmission increases. The commercial pressure to maximize yield per unit volume pushes density toward welfare-compromising levels. Certification schemes that set maximum density limits provide a welfare floor, but the science suggests that even certified densities may be above welfare-optimal levels for salmon. Investing in water quality management and reduced density is a direct welfare improvement for billions of farmed fish annually.