Controlling salmon lice on farmed salmon and implications for wild salmon.

Abstract This review documents the extent to which management of salmon lice ( Lepeophtheirus salmonis ) on farms has a measurable impact on the health of wild salmon. The salmon louse is a persistent and often severe parasite of farmed salmon throughout the Northern Hemisphere. High farm densities in some areas have led to lice levels within adjacent wild salmon populations that are higher than occur naturally. To minimize the additional infection pressure of the parasite on wild salmon, aquaculture industries adopt strategies of integrated pest management that include systematic monitoring, treatment, locating farms to minimize exposure to lice and maintaining optimal stock densities and single year-classes. Often these management activities are coordinated among farms within a region. A number of national or regional programmes collect and publicize salmon louse infection data from farmed and wild salmon. Some but not all management programmes show evidence of reducing infection levels on wild salmon; however, the available data are not yet sufficient to make firm conclusions regarding population effects. The local management and conservation of wild salmon populations should continue to be coordinated and integrated as the abundance of these fish is influenced by climatic, oceanographic and anthropogenic factors, including but not limited to salmon aquaculture.