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Photo: The Norwegian Seafood Export Council.Photo: The Norwegian Seafood Export Council

Undesirable substances in farmed fish ?

14.02.2014 // The National Institute of Nutrition and Seafood Research (NIFES) has carried out analyses to determine the content of drug residues and other undesirable substances in farmed fish for over a decade.

Since the analyses were initiated in the late 1990s, residues of illegal drugs have only been found in one sample of farmed fish, and the level of approved drugs and other undesirable substances analysed has been below internationally accepted limits in all species of farmed fish investigated. The same trend was observed through analyses of drug residues in farmed fish from 2012. The monitoring results also showed low levels of organic contaminants and heavy metals in farmed fish fillets compared to the EU’s upper limits for the analysed compounds, where such limits exist. The surveillance activities document good seafood safety with respect to drug residues and other undesirable substances in farmed fish. 

On behalf of the Norwegian Food Safety Authority, NIFES has under its surveillance programme for the monitoring of undesirable substances in farmed fish determined the content of residues of illegal drugs, legally used veterinary medicines and other undesirable substances. According to Directive 96/23/EC the minimum number of samples to be taken each year is 1 sample per 100 tonnes produced fish. In 2012 this applied to all farmed fish species: Atlantic salmon, rainbow trout, Arctic char, turbot, Atlantic halibut, Atlantic cod and wolf-fish. Analyses were carried out on individual or pooled samples of a total of  11585 farmed fish harvested that year. The report can be found here: http://www.nifes.no/file.php?id=2097. The levels of undesirable substances in fillets of farmed fish generally reflect to a large extent the feed given to the fish. To ensure the safety of the fish feed, the Norwegian Food Safety Authority has its own monitoring programme for undesirable substances in feed and feed materials. 

Drug residues

In 1998, Norway introduced a comprehensive control system to ensure that farmed fish for consumption do not contain residues of illegal pharmaceuticals or residues of legal pharmaceuticals in concentrations above internationally accepted levels. The system is based on the control and registration of the use of pharmaceuticals, enforcement of withdrawal times to ensure that fish are not slaughtered until a certain fixed period of time has elapsed after administration of the pharmaceutical, and analytical control of residues of pharmaceuticals in the farmed fish. The Norwegian system for control and analysis of pharmaceuticals and environmental pollutants in farmed fish complies with EU regulations, and is regularly monitored and revised by EFTA’s monitoring body ESA. The analytical control of residues of pharmaceuticals in farmed fish forms part of the surveillance programme for monitoring of undesirable substances

In the 2012 monitoring programme, samples of farmed fish to be analysed for pharmaceuticals, illegal substances, and contaminants were collected on farm sites by official inspectors. Farm sites from all regions with aquaculture activity, and at least 10% of the total number of sites were included in the sampling plan. The sampling plan was randomised with regards to season and region, and the sample identification was blinded for the analysts. The 30 analytes included, ranged from approved delousing agents and antibiotics, to illegal drugs. As in previous years, the level of approved drugs was well below internationally accepted limits. However, of the therapeutic agents in group B, emamectin was detected in two of the 68 pooled samples, and cypermethrin was found in one of the 16 pooled samples of farmed fish analysed in 2012. The highest concentration of emamectin was 18 µg/kg, and the level of cypermethrin was 15 µg/kg, which are both below the MRLs of respectively 100 μg/kg and 50 μg/kg. 

Residues of other undesirable substances

The results from the monitoring of undesirable substances in farmed fish for 2012 show that the levels of organic contaminants and heavy metals in farmed fish fillets are low compared with the EU’s upper limits, where such limits exist. Organic compounds such as dioxins and dioxin-like PCBs are fat-soluble environmental pollutants found primarily in fatty fish. The mean content of dioxins and dioxin-like PCBs in the samples analysed was less than1/10 of the EU’s upper limit. Mercury is an environmental pollutant which is absorbed and stored in both fatty and low-fat fish. The average level of mercury in all of the samples analysed was less than 1/30 of the EU’s upper limit. In order to maintain food safety, it is important to monitor the level of these substances in fish for consumption.


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