The sublethal toxicity of the sea lice chemotherapeutants SLICE® and Ivermectin to juvenile Starry Flounder (Platichthys stellatus)

Open net-pen Atlantic Salmon (Salmo salar) aquaculture is an important part of Canada's aquaculture industry. SLICE® (a.i.: emamectin benzoate [EMB]) and ivermectin (IVM) are two chemicals used in salmon aquaculture to treat and prevent sea lice infestations that can adversely affect fish health and yield. The sublethal toxicity of these chemotherapeutants on behavioural, physiological and biochemical endpoints was assessed using juvenile Starry Flounder (Platichthys stellatus) exposed to treated sediment. Significant concentration-dependent reductions in burst swim performance and aerobic scope were found when fish were exposed to IVM and the combination IVM/EMB. Significant reductions in burrowing behaviour, evidence of avoidance of treated sediment, and significant increases in darkened skin colouration and reduced camouflage ability were also observed for exposures to EMB, IVM and the combination of both at concentrations that may be found in the environment. These findings will lead to developing guidelines for acceptable environmental chemotherapeutant concentrations protective of wild flatfish.