A salmon farm in the North Atlantic Photo: British Columbia Salmon Farmers Association

The severity of side-effects caused by vaccinating salmonids depends on the species and the composition of the vaccine, a study has found.

Oil-based vaccines are used in aquaculture to provide fish with life-long immunity against bacterial infections. However, they often have side-effects such as pigmentation and adhesion between internal organs, which can reduce carcass quality at slaughter.

A study by researchers at the Norwegian School of Veterinary Science has found that some species of salmonid, such as the Atlantic salmon, cope with vaccination much better than others. Another important factor is the composition of the vaccine: less refined vaccines produce the most severe side effects.

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