Farm-raised salmon are free of sea lice when they are entered into the ocean, but during the fall adult wild salmon may pass sea lice to farm-raised salmon.
Sea lice are naturally occurring parasites found on many species of marine fish, pose no risk to humans, but may harm tiny juvenile salmon. Salmon farmers have several ways to reduce or eliminate sea lice on their fish so they are not an additional source of infection during the springtime outmigration of juvenile wild salmon. Management techniques can include medicinal (emamectin benzoate by feed) and non-medicinal (freshwater bath, hydrogen peroxide, water pressure). Research into cleaner fish is currently underway.