Sea lice infestation is one of salmon aquaculture's most significant welfare problems. Selective breeding for genetic resistance to lice is an emerging long-term solution with major welfare implications.
Genetic approaches to sea lice resistance represent a promising welfare improvement that addresses the problem at its source rather than through repeated stressful treatment events. Chemical treatments for lice require handling and bathing salmon in medications that are themselves stressful and sometimes harmful. Biological controls using cleaner fish like wrasse and lumpfish have welfare implications for the cleaner fish themselves. Salmon with genetic resistance that prevents lice establishing would eliminate much of the treatment burden while reducing lice welfare harm.