Biological Hazards

Genetically Modified Sterile Salmon - Risk Assessment of Field Trials


Report no: 2023: 20

Published: 06.10.2023

Key message:

VKM has assessed the risk to biodiversity in Norway in relation to the release of 303 genetically modified farmed salmon for use in field trials.

The Norwegian Environment Agency commissioned this risk assessment.

Gene flow from escaped farmed salmon to wild salmon poses a problem to the wild salmon populations in Norway. To address this issue, the Institute of Marine Research has developed a salmon that is designed to be sterile, by using the genome editing technique CRISPR.


VKM has assessed whether the field trial release of 303 genetically modified farmed salmon and 485 control salmon could have potential negative impacts on biodiversity in Norway. According to the application, the fish will be kept in sea cages, and VKM has assessed the risk they pose both in the cages and in case of their escape from these.

VKM concludes that, based on the documentation in the application, there is insufficient proof of sterility in all of the 303 genetically modified salmon and likewise, a possibility that an unknown number of the 485 fertile controls may carry a mutated allele that leads to sterility. In a worst-case scenario these alleles could be introduced to wild salmon populations, should the salmon escape from the net pens.

VKM’s risk assessment will be part of the knowledge base the Environmental Agency will use in their final evaluation of the application.

The original risk assessment was approved by an interdisciplinary approval group and published on October 6th, 2023.

Assignment update

Answer from VKM to the added request by the Norwegian Environment Agency on 8. April 2024

The Environment Agency has asked VKM to evaluate whether new documentation provided by HI (in February and March 2024), will affect the conclusions made by VKM in the risk assessment of genome-edited sterile salmon to be used in the field research trial.

The new documentation from HI includes additional genotyping results, i.e., data clarifying the genetic variants (mutations) of each individual experimental fish. In addition, HI has provided analyses of tissue samples (histological analyses) from dissected fish, confirming absence of germ cells in fish with genetic variants causing sterility.

VKM concludes

Based on the new data, VKM concludes that there is considerably lower uncertainty related to whether or not the experimental fish are sterile. However, VKM considers all research trials which could introduce heritable sterility into wild salmon populations as having a potentially high risk due to the inherent possibility of causing a massive negative environmental impact.

Therefore, VKM upholds the conclusion of risk category “potentially high risk” even though the likelihood (“very unlikely”) of the genome-edited salmon having a negative impact on wild salmon has been reduced.

Click here Pdf, 312 kB. to read the response to the Norwegian Environment Agency.


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