Some of the undesirable substances that are found in fish feed can be transferred to the edible part of the fish and affect food safety.

Norwegian and European food authorities set maximum levels for undesirable substances in feed and fillet and regulations for monitoring. Research and understanding how the undesirable substances are transferred from feed to fillet are important factors in determining any potential risk to the consumer.

Models can provide the answer

One way to study the transfer of substances is to make mathematical models of how much of the undesirable substance will be transferred from the feed to the fillet. A model like this can be used to predict how much of a substance will be transferred to the fish given a known amount of the substance in the feed. These models are useful in risk assessment and for advising food authorities. For example, we can calculate whether an undesirable compound in the feed will entail a risk to the consumer, what level the feed has contained if the substance in the food has exceeded the limit and the sources that may have caused the contamination.

What substances are transferred?

At present, there are few studies on the transfer of substances from feed to food. However, such studies will enable more systematic regulations to be drawn up in future. This means that compliance with maximum limits in feed will automatically mean compliance with maximum limits in food, given that we know how much is transferred from feed to food.

NIFES has studied the degree of transfer of certain substances from fish feed to the edible part of the fish:

Degree of transfer of certian substances

The table shows the degree of transfer of certain substances from fish feed to the edible part of the fish
Substance groupTypeTransfer degree
ToxapheneEnvironmental contaminantsmedium
EnrofloxacinAntibacterial substances from animal by-productslow
Ciprofloxacin from enrofloxacinAntibacterial substances from animal by-productslow
Inorganic mercuryHeavy metalslow
HBCDEnvironmental contaminantshigh
Polychlorinated dibenzodioxin (PCDD)Environmental contaminantshigh
Polychlorinated dibenzofuran (PCDF)Environmental contaminantshigh
Dioxin-like polychlorinated biphenyl (PCB)Environmental contaminantshigh
Organic arsenic (water-soluble)Heavy metalshigh
Organic mercury Heavy metalshigh
EthoxyquinAdditives low
Ethoxyquin dimer from ethoxyquinAdditives medium

The degree of transfer is defined as high, medium, low and negligible in the table. This is based on dioxins and PCB, as a high level of these are retained in the fish.

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