Monitoring OF pharmaceutical substances in Norwegian farmed fish

Bjørn Tore Lunestad*), Ole Jakob Nøstbakken, Helge Torbjørn Hove, Ingvild Eide Graff, Amund Måge, Lise Madsen and Rita Hannisdal
*) National Institute of Nutrition and Seafood Research (NIFES)
Strandgaten 229
N-5817 Bergen
Norway
blu@nifes.no

The production of farmed fish in Norway reached 1.33 million tonnes measured as round weight in 2014, of which the main species were Atlantic salmon (Salmo salar). During their life cycle, the farmed fish may be subjected to infectious diseases of different etiology mediated by virus, bacteria or parasites. Hence, application of therapeutic agents is occasionally required.  

The Norwegian system for monitoring of pharmaceutical substances in farmed fish, is based on several components. Central elements are mandatory licensing of fish farms, strict regulations for prescription of therapeutics by veterinarians or fish health biologists, submission of information on drug dispersion from approved feed mills or pharmacies, mandatory notification prior to slaughtering, and analytical examination for drug residues.

Since 1998, The National Institute of Nutrition and Seafood Research (NIFES) has conducted annual analytical monitoring of farmed Norwegian fish for the presence of residues of approved and illegal pharmaceutical substance and contaminants.  The monitoring program has been initiated and financed by the Norwegian Food Safety Authority (NFSA) in accordance with the current EU regulations (Directive 96/23/EC).  NFSA provides the samples, whereas NIFES is responsible for the analysis, applying methods accredited after the ISO-17025 standard as  well as for reporting of results.

During 2014, samples from a total of 13 180 farmed fish were collected. Samples to be examined for illegal substances were collected by official inspectors during all stages of farming and without prior notification. About 35% of these samples was analyzed for substances with anabolic effects or other unauthorized therapeutics. Metronidazole was detected in fish from one farm. The findings were reported to the NFSA, which concluded that the samples had been contaminated. No other residues of unauthorized substances was detected.

Samples tested for legally applied veterinary drugs were collected at processing plants, and are thus representative of Norwegian farmed fish ready for the market. Emamectin was detected in two out of 106 pooled samples. The highest concentration measured was 9.7 μg/kg, which is well below the current Maximum Residue Limit (MRL) of 100 μg/kg. Cypermethrin was also found in two out of 34 pooled samples. The highest level measured was 11 μg/kg, while the MRL for cypermethrin is 50 μg/kg. No other veterinary drug residues were detected in 2014.