The potential of carbaryl as a treatment for sea lice infestations of farmed Atlantic salmon, Salmo salar L

Summary The treatment of sea lice, Lepeophtheirus salmonis infestations on farmed Atlantic salmon, Salmo salar requires regular bathing of the fish in diachlorvos (DDVP), 2,2‐dichlorovinyl dimethyl phosphate, with subsequent release to the marine environment of spent pesticide. The toxicity of a possible alternative compound, carbaryl, l‐naphthyl N‐methylcarbamate) to kill sea lice and Atlantic salmon was examined. Preliminary studies with carbaryl indicate the potential advantage of a reduced treatment dose was outweighed by the greater persistence of both the parent compound and of its toxic degradation product. Hence this carbamate insecticide is unlikely to be considered by regulatory authorities as an alternative treatment for sea lice infestations.