Anti-sea lice agents in Norwegian aquaculture; surveillance, treatment trends and possible implications for food safety

Sea lice are a major challenge for Norwegian aquaculture, and to cope with sea lice infections, several physical, biological and chemical treatments are applied. This study presents data on the use of anti-sea lice agents for Norwegian farmed fish from 1992 to 2017 and results from the surveillance of residues of such agents in samples collected from 2002 to 2017. In the period 2002–2007, the use of anti-sea lice agents included emamectin, cypermethrin and deltamethrin. Azamethiphos and flubenzurons were introduced in 2008 and 2009, respectively. In the ongoing surveillance of Norwegian farmed fish, more than 3000 pooled samples have been examined for residues of anti-sea lice agents in the period from 2002 to 2017. Residues were detected in 3% of the samples. Emamectin was detected in 5.0% of the samples analyzed for emamectin, while cypermethrin was detected in 2.1% of the samples analyzed for cypermethrin. Furthermore, residues of diflubenzuron and teflubenzuron were detected in 1.2 and 0.1% of the samples analyzed for these compounds, respectively. None of the other anti-sea lice agents were detected. No measurements were above the respective maximum residue limit (MRL) set by the EU.