An updated review of hazards associated with the use of pesticides and drugs used in the marine environment by the finfish aquaculture industry in Canada

Abstract

The purpose of this CSAS document is to update the current knowledge relating to the exposure and potential biological effects (hazards) of pesticide and drugs used in the marine environment on non-target organisms during finfish aquaculture activities. This document will provide peer reviewed science advice to DFO’s Aquaculture Management Directorate. In this paper we reviewed the available literature on biological effects of two pesticide formulations currently in use in Canada: Salmosan® (active ingredient: azamethiphos) and Paramove 50® (active ingredient: hydrogen peroxide) In general, new peer-reviewed published data (since 2013) are relatively rare although there are a number of relevant documents in the grey literature. In 2013 we concluded that the degree of toxicity was pesticide specific with Paramove 50® being the least toxic of these formulations. Recent publications show, however, that sublethal responses to Paramove 50® may occur in shrimp and mysids at low concentrations. Anti-parasitic drugs were not part of the 2013 CSAS review process. Available data are reviewed dealing with lethal and sublethal responses (moulting, growth and behaviour) of non-targets to emamectin benzoate (EB) and ivermectin. Two new compounds, selamectin and lufenuron are mentioned but next to no data are published regarding these compounds and aquaculture use. Finally, a section on antibiotics is presented focusing on biological effects. The concentration of these compounds required to affect non-targets is often greater than the prescribed treatment levels. The key concern with antibiotic use in aquaculture is the potential for antibiotic resistance to develop both in the target species, fish and in the microbial populations in the marine environment. This topic will be covered in a separate CSAS research document. There remain inconsistencies with respect to biological effects research and anti-parasitic compounds. Some authors use technical grade chemicals, others use anti-sea louse formulations. Authors, surprisingly, still are able to publish effects data using nominal concentrations with no analytical chemistry conformation of concentrations. While there are recommended treatment doses of therapeutic drugs (anti-parasitic and antibiotic), there are no labels prescribing use as there are for pesticides. The experience and expertise of prescribing veterinarians plays a major role in how fish are treated, and courses of treatment can vary considerably.