Effects of pharmaceuticals used to treat salmon lice on non-target species: Evidence from a systematic review

Abstract

Aquaculture is currently one of the best prospects to help meet the growing need for protein in the human diet. However, aquaculture development and production result in consequences for the environment and also impact other productive activities. Salmon and trout cage culture has required the use of large quantities of pharmaceuticals in order to control outbreaks and the persistence of different pathogens, including sea lice (parasitic copepods), which cause economic losses of around 0.39 € Kg−1 of salmon produced. The pharmaceuticals currently used for the control of sea lice (cypermethrin, deltamethrin, azamethiphos, hydrogen peroxide) are applied by in situ immersion treatments, enclosing net pens using tarpaulin and then bathing fish with the pharmaceutical. After treatment the pharmaceuticals are released into the surrounding environment, exposing non-target species. Although the effects of such pharmaceutical exposure has been studied in some species, to date a systematic and exhaustive review of these potential effects has not yet been performed. In this study, an exhaustive review of the literature evaluating lethal and sub-lethal effects of anti-sea lice pharmaceuticals on non-target crustaceans and bivalves was performed, in order to assess the extent of the effects, toxicity, variables affecting such toxicity and identify potential synergistic effects previously unexplored. Our results show clear negative effects at concentrations lower than those used in treatments against sea lice in all of the species studied. Likewise, this study demonstrates knowledge gaps that need to be addressed in order to improve our understanding of the effects of these pharmaceuticals on non-target species, ecosystems in general and other productive activities.