Stocking density in sea pen salmon farming is one of the most important welfare variables. Understanding what the science says helps evaluate certification claims.
Sea pen stocking density is a welfare lever with clear scientific evidence: lower densities produce better welfare outcomes across multiple indicators. Salmon at high densities show more fin damage, higher cortisol levels, more aggressive interactions, and faster disease transmission. The economic logic of intensive farming pushes toward higher densities, while the welfare logic pushes in the opposite direction. Welfare certification that sets and verifies density limits creates the market mechanism for maintaining lower-density production. Consumer choice of certified salmon provides the financial signal that makes lower-density farming economically viable.