Sensitivity of Atlantic salmon to the pesticide pirimiphos-methyl, present in plant-based feeds

Abstract The use of plant-based feeds has introduced undesirables, such as pesticides, that have previously not been associated with seawater farming of fish species such as Atlantic salmon. Earlier wide-scope chemical screening showed that the organophosphate (OP) pirimiphos-methyl (PM-m) is one of the most prevalent pesticides present in commercially produced Atlantic salmon feed. Information on the safe upper limit of background levels of PM-m in Atlantic salmon feeds with regards to possible adverse effect on fish health is lacking. Therefore, Atlantic salmon (132 ± 25 g) were fed graded levels of PM-m spiked feeds (0, 0.35, 1.5, 5, and 22 mg kg−1) in triplicate for 3 months. Adverse effects were assessed on OP target toxic exposure such as plasma choline esterase (ChE), and secondary toxic responses such as lipid metabolism and oxidative stress, as well as general adverse effect parameters (plasma biochemistry, haematology, and growth). Safe limits were set by model-fitting the effect data in a dose-response (lower bound) bench mark dose (BMDL) regression analysis. Fish fed 1.5 mg kg−1 and higher had a significant (p