Anti‐Sea Lice Veterinary Medicinal Products on Salmon Farms: A Review and Analysis of Their Usage Patterns, Environmental Fate and Hazard Potential

ABSTRACT Aquaculture is expanding globally and the environmental implications associated with this growth, including the increasing use of chemicals in aquatic locations, are an emerging concern for environmental legislators. Veterinary medicinal products (VMP) are used as chemotherapeutants to control sea lice infestations on open‐net pen salmon farms and questions have been raised about their potential to cause adverse effects on marine ecosystems. The current study analyses the usage patterns of anti‐sea lice VMPs in major salmonid aquaculture regions and reviews the current knowledge on their mode of action, routes into the environment and environmental fate. We subsequently evaluate their hazard potential by performing a toxicity assessment and deriving up‐to‐date preliminary environmental quality standards (EQS). We demonstrate that the use of anti‐sea lice VMPs varies between the major salmon‐producing countries, with quantities varying over time and depending on the chemical. Norway and Chile use the highest quantity of chemical treatments, consistent with their higher salmon production capacity, and while the reliance on some chemicals has decreased the use of newly authorised chemicals has increased. Our toxicity assessment revealed that there was sufficient reliable acute toxicity data to derive EQS for five of the selected anti‐sea lice VMPs using the probabilistic method of constructing species sensitivities distribution curves. However, insufficient chronic and sediment toxicity data were available for all chemicals and therefore EQS were derived using the traditional deterministic method. The information presented in this review can guide future research and facilitate better environmental risk assessments of chemotherapeutant used on salmon farms.