Sea lice (Lepeophtheirus salmonis and Caligus spp.) are a common ectoparasite on farmed Atlantic salmon (Salmo salar). Damage from sea lice and management of the parasite cost an estimated $1.25 billion per year to the industry with Norway, Scotland and Chile being the most impacted countries globally. The free-swimming planktonic larvae disperse through the sea whereas the chalimus, pre-adult and adult stages settle on salmon and are parasitic and feed on the mucous, skin, and tissues of salmon.
The welfare of infected salmon is poor with sea lice causing injuries, reductions in osmoregulatory capability, a lower immune capacity, increased stress, reduced growth and can result in death. Many sea lice management methods are available to the industry. Research of these methods tends to focus on their effectiveness with little attention given on the welfare risks associated with sea lice management methods. Sea lice management methods can be grouped into two categories: prevention or treatment. We will review the welfare risk of common prevention and treatment methods by discussing the mortality and injury risks of each methods as well as discussing other welfare concerns associated with each management method. This welfare risk assessment will be put in the context of the methods’ effectiveness and their environmental impact.