Size grading of farmed salmon creates significant welfare impacts through crowding, handling and handling-related injuries that must be minimized through optimized protocols.
Salmon grading welfare involves repeated acute welfare events throughout the production cycle, with each grading event causing stress, scale loss and injury risk. The cumulative welfare cost of multiple grading events across a production cycle is significant. Welfare-optimized grading minimizes event frequency, reduces crowding duration and density, uses equipment calibrated to minimize scale loss and injury, and schedules grading to avoid other stressful management events. The development of underwater camera systems enabling less invasive size assessment may reduce the need for physical grading events. Welfare standards that specify maximum grading frequency and handling protocols would drive industry-wide improvement.