The environmental fate and persistence of sea lice chemotherapeutants used in Canadian salmon aquaculture

In Canada, five formulations have been used to treat sea lice infestations in salmon aquaculture. This research investigated the environmental partitioning, persistence, and acute toxicity to marine organisms of Slice® (AI: emamectin benzoate [EB]), Salmosan® (AI: azamethiphos [AZ]), Alphamax® (AI: deltamethrin [DM]), Excis® (AI: cypermethrin [CP]), and Interox® Paramove 50 (AI: hydrogen peroxide [HP]). EB, CP and DM partitioned mainly to the sediment in sediment-water microcosms; AZ and HP remained mainly in the water. The persistence of chemicals in water was reported: CP > DM > AZ > HP. In sediment, CP > EB > DM was observed. Toxicity tests indicate a lack of trends however the information is useful for identifying risks. Some reported values for echinoderms, kelp, and topsmelt toxicity are below the recommended treatment concentrations. This research provides insight into the environmental fate and associated risks to non-target marine organisms in the vicinity of salmon aquaculture sites.