Sea lice are marine ectoparasites that are adapted to live on fish, feeding on their skin and blood to survive. Sea lice have a short, free-swimming larval phase, and a longer attached parasitic phase. At BC CAHS, fish are examined for the presence of sea lice in any life stage. Two species are common in BC, Lepeophtheirus salmonis, which is most commonly found on salmon, and Caligus clemensi, which is found on many different fish species. This information can be used by fish health professionals to monitor sea lice levels in different regions over time, and can be conducted as part of sea lice and fish health audits.