Ectoparasite Reduction

The present invention relates to exposing aquatic ectoparasites to an aqueous solution comprising hydrogen peroxide and exposing the aquatic ectoparasite to sound waves. Claimed is a method of injuring or killing an aquatic ectoparasite; a method of reducing aquatic ectoparasitic infestation on an aquatic animal; and a non-therapeutic method of improving the appearance, meat quality and/or growth rate of an aquatic animal. Also provided is an apparatus and a kit of parts comprising an aquatic enclosure for retaining the aquatic animal and an aqueous solution comprising hydrogen peroxide, and a means for directing sound waves into the aquatic enclosure. Also claimed is hydrogen peroxide for use in the method of treating ectoparasitic infestation of an aquatic animal. Decomposing hydrogen peroxide may form bubbles 12 on or near the surface of the animal. These bubbles collapse when exposed to sound waves 13 to generate a liquid jet which has sufficient energy to dislodge or kill ectoparasites on the surface of the animal. The animal may be fish such as salmon, and the aquatic ectoparasites may be sea lice.