Little disease transmission from farmed fish to wild salmonids says study

Editorial Staff

Annually, the Institute of Marine Research checks whether wild salmon and sea trout are affected by four selected viruses from farmed fish. 

A study conducted last year by the Norwegian Institute of Marine Research has revealed minimal viral and bacterial transmission from farmed to wild fish.

The research focused on migrating wild salmon (post-smolt) and sea trout, examining them for four viruses commonly found in farmed fish and, for the first time in 2023, the bacterium Renibacterium salmoninarum.

Out of 138 wild fish tested, a few tested positive for viruses such as SAV, ILAV, PRV-1, and PMCV, but none for Renibacterium salmoninarum. However, the virus levels found were very low, suggesting possible false positives.

The study targeted areas with high farming activity, including Boknafjorden, Hardangerfjord, and areas around Hitra, to assess the impact of farming on wild fish infections. Despite recent outbreaks of bacterial kidney disease (BKD) caused by Renibacterium salmoninarum in farming facilities, none of the wild fish examined were found to be infected.

Researcher Abdullah S. Madhun reported that the findings support previous results, indicating a very low incidence of infection in migrating wild fish and suggesting that wild fish are not significantly affected by infections prevalent in fish farming.

The study, part of a monitoring program mandated by the Norwegian Food Safety Authority, aims to understand the transmission dynamics between farmed and wild fish, particularly in the context of salmon lice monitoring.


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