Pesticide residues in aquaculture salmon filet and feed: Quantitative and qualitative screening profiles of legacy and current-use pesticides using GC-EI-MS/MS and LC-ESI-IMS-QToF

In recent decades, the ingredients used in aquaculture feeds have changed from marine-based to more plant-based. As a result, the content of legacy, organochlorine pesticides has decreased, but the potential increase of current use, land-based pesticides has not been documented. In this work, two analytical techniques were developed and applied to characterize the pesticide profile in current Norwegian salmon aquaculture after the shift to more plant-based feed ingredients. Samples of salmon filet, feed, and feed ingredients were analyzed using two different chromatographic methods, a quantitative gas-chromatography-triple quadrupole mass spectrometry method (43 analytes) and a broader, presence/absence screen using liquid chromatography-high resolution mass spectrometry (215 analytes). Among all samples and between both methods, a total of 43 different pesticide analytes were identified. Results show that the major pesticides present in the filet of farm-raised salmon are the legacy, organochlorine pesticides as contaminants. Conversely the feed is dominated by current-use, organophosphate and pyrethroid pesticides. There were no exceedances of the few established maximum residue limits for contaminants in fish and feed. No pesticides in salmon filet exceeded the default limit of 10 μg/kg, while there were several observations in feed above this level. These results suggest low risk in terms of food safety, however, issues related to animal health cannot be ruled out. The two chromatography methods are compared, and they complement each other by giving an overview of pesticides with both breadth and depth.