Sea lice treatments for farmed Atlantic salmon require balancing the welfare harm of the lice themselves against the welfare costs of treatment methods, with newer approaches seeking to reduce harm on both sides.
Sea lice treatment welfare involves a genuine dilemma: leaving lice untreated causes progressive welfare harm, while most available treatments cause acute welfare costs through handling, chemical exposure, or thermal stress. The ethical calculus favors treatment when infestation is established, but minimizing treatment frequency and selecting less aversive methods remains a welfare priority. Genetic approaches that produce sea lice resistant salmon would resolve this dilemma by preventing infestations rather than treating them, representing the most welfare-positive long-term solution. Investment in resistance genetics is therefore simultaneously a commercial priority and one of the highest-impact fish welfare interventions available.