A Review and Assessment of Environmental Risk of Chemicals Used for the Treatment of Sea Lice Infestations of Cultured Salmon

Abstract

Chemicals (sea lice therapeutants) currently authorized in North America and Europe for the treatment of sea lice infestations in cultured salmon may be classified into two major groups. The classification is based on their routes of administration, and includes bath techniques (organophosphates, pyrethroids and hydrogen peroxide) and additives in feed (avermectins, chitin synthesis inhibitors). The ecological risk posed by the use of the chemicals is reviewed and assessed in this chapter.While the biological ef- fects of sea lice therapeutants on aquatic animals that may live near salmon culture sites have been studied under laboratory conditions, field studies on the efficacy, fate and dis- tribution, and biological effects are limited. In general, the in-feed treatments are more convenient to administer and posed less ecological risk than the bath treatments. As an example, the approach adopted by the UK was used to assess the environmental safety of the sea lice therapeutants. It was concluded that there are considerable differences between the environmental characteristics of fish farmsites and their ability to accept dis- charges of sea lice treatments without giving rise to unacceptable environmental impacts. Such site-specific risks can be managed through the application of appropriate environ- mental quality standards for the chemicals concerned, and site-specific assessment of the maximum acceptable rate of use of the treatments.