A large, natural infection of sea lice on juvenile Pacific salmon in the Gulf Islands area of British Columbia, Canada

High levels of sea lice generally exceeding a prevalence of 60% were found on all species of juvenile Pacific salmon and on juvenile Pacific herring in the Gulf Islands area within the Strait of Georgia, British Columbia. Virtually all sea lice were Caligus clemensi and most stages were maturing or mature. There are no active fish farms in this area, indicating that this is a naturally occurring epizootic of sea lice. It is possible that the infection was associated with Pacific herring that spawned in the area in the spring, although the linkage between the spawning Pacific herring and the infection on Pacific salmon was not determined.