Can pesticides end up in salmon?

Over half of the fish feed ingredients used today come from plant meal and oils and with these, also pesticide residues that are currently used on crop.

We are now seeing much less of the ‘old’ environmental contaminants like dioxins and DDT in farmed salmon, after plant ingredients replaced fish oil and meal in the feed. Is it possible, though, that we have created a new problem caused by pesticides from agriculture ending up as residues in fish feed?

 

Over half of the fish feed ingredients used today come from plant meal and oils and with these, also pesticide residues that are currently used on crop. With about a thousand registered pesticides worldwide, it is feared that some of these may end up in the feed of farmed salmon and eventually in the fillet on your dinner plate.

The ingredients in plant feed come from all over the world and the huge number of different pesticides make it difficult to know what to look for. Identifying the pesticides that may have ended up in Norwegian fish feed has taken a lot of detective work.

Pesticides can end up in fish feed

Commercial salmon feed currently uses plant products such as rapeseed oil, corn gluten, soya protein and wheat meal, and most of these ingredients are imported from other countries.

Agriculture is subject to restrictions concerning what may be used of pesticides to prevent fungi, insects and diseases on the plants, and we follow the EU regulations in this area. Countries outside the EU often have other restrictions and since many of the feed ingredients are imported, you can find both residues of known pesticides from European agriculture and potentially also residues of pesticides that are not used in the EU.

Pesticides are commonly found in fruit, vegetables and meat

The Norwegian Food Safety Authority has monitored pesticide residues in food since 1977, and these have particularly been found in fruit, berries, herbs and vegetables*. Pesticide residues are also found in livestock feed used in agriculture, and the Food Safety Authority monitors the levels of pesticides in meat, milk, eggs and other animal products. **

The matter of pesticides in salmon farming is relatively new, however, since plant ingredients in commercial fish feed have increasingly replaced marine feed ingredients the past 20 years.  

New method of identifying pesticides in salmon feed

Using new analysis tools, scientists at the institute of marine research (IMR) have been able to screen for around 150 important pesticides. The scientists found residues of between five and seven pesticides commonly present in commercial fish feed, including residues of pirimiphos-methyl, tebuconazole and chlorpyriphos-methyl. All of the substances found are legal to use in Norway and the EU and maximum limits have been stipulated for residue concentrations in food but not feed yet

The levels of pesticide residues in feed are generally low, but there is nonetheless cause to be vigilant. Pesticides are designed to eliminate insects, pests and fungi, among other things, and there is concern about their potential biological adverse effect on fish, and whether residues and breakdown products end up in the salmon fillet.

Pesticides affect fish health

Other trials have been able to show that pesticide residues clearly affect fish health. Trials on both cell cultures and on live fish have shown that the pesticides in question affect the normal formation of fatty acids.

‘We do not want to interfere with the normal fat profile of fish, since this may harm the fish. The question is how much of these undesirable substances the fish tolerates. We must also look  for a certain cocktail effect, meaning how the various substances affect each other,’ says Marc Berntssen, senior scientist at NIFES.   

‘We have now been able to identify which pesticides are found in salmon feed and shown that these may have a negative effect on fish health, but we have not yet found out how low the level must be to avoid harm to the fish,’ he says.

More knowledge required about pesticide residues in fish fillets

Despite finding pesticide residues in feed, the scientists at NIFES have not yet found pesticides in the salmon fillet.

‘It is not surprising that we haven't found pesticides in the fillet, since these pesticides are easily broken down. This means that the pesticides are not directly transferred from the feed to the fillet, but we cannot rule out the possibility of finding converted pesticide residues, known as degradation products, in further studies. It is therefore vital that we continue work on identifying pesticides and degradation products and the consequences of these ending up in the feed,’ says Berntssen.


Facts:

•    More than 55 per cent per cent of feed ingredients in commercial salmon feed come directly from plant oils and meal.
•    IMR has analysed samples from 19 types of Norwegian and English commercial feed for Atlantic salmon, and 13 commercial feed ingredients.
•    Findings include:
o    Pirimiphos-methyl in 14 of the feed samples
o    tebuconazole in 6 of the feed samples


Sources:

*the Norwegian Institute of Public Health
**Matportalen.no