Abstract: A method for removing ectoparasites, such as sea lice, from a fish in water, comprising: (i) administering a neonicotinoid to remove the ectoparasites from the fish; and (ii) exchanging the water comprising the removed ectoparasites with replacement water, thereby separating the removed ectoparasites and the fish. The neonicotinoid is not imidacloprid, and is not configured or formulated for in-feed administration. The fish may be a salmonid, char, or cleaner fish, and the neonicotinoid may be applied at a sublethal dose and/or for a sublethal time, at a lethal dose and/or for a lethal time, or at a dose that knocks down the ectoparasites. The method may further comprise the step of preventing release of the removed ectoparasites into the environment, for example by collecting the ectoparasites from a sample of water comprising the removed ectoparasites, for example by passing the sample through a filter, preferably a mesh filter. A neonicotinoid for use in the method is also provided.

Abstract: A method for removing ectoparasites from a fish in water may comprise administering to the fish a neonicotinoid to remove the ectoparasites from the fish and exchanging the water comprising the neonicotinoid and the removed ectoparasites with replacement water, thereby separating the removed ectoparasites and the fish. The method may comprise the further step of preventing release of the removed ectoparasites into the environment, for example by passing sample of the water comprising the removed ectoparasite through a mesh filter. A neonicotinoid may be used in treating an ectoparasite infestation in a fish, and a composition for use in treating an ectoparasite infestation in a fish may comprise one or more ectoparasiticides, wherein one of the one or more ectoparasiticides is the neonicotinoid, is provided. The neonicotinoid may be imidacloprid. In use, the dosage regime may be sublethal and/or lethal.